Pub Date : 2024-09-13DOI: 10.1103/physrevmaterials.8.095401
A. F. Baumann, D. Mutter, D. F. Urban, C. Elsässer
Mechanical stresses and strains in the microstructure of cathode materials evolving during charge/discharge cycles can reduce the long-term stability of intercalation type alkali-metal-ion batteries. In this context, crystalline compounds exhibiting zero-strain (ZS) behavior are of particular interest. Near-ZS sodiation was experimentally measured in the tetragonal tungsten bronze (TTB) type compound . Using a first-principles method based on density functional theory, we investigate the potential of iron-based fluoride compounds with tungsten bronze (TB) structures as ZS cathode materials. Simulations were conducted to study the intercalation of the alkali metal ions , and into the TTB and two related TB structures of the cubic perovskite and hexagonal types. We describe compensating local volume effects that can explain the experimentally measured low volume change of . We discuss the structural and chemical prerequisites of the host lattice for a ZS insertion mechanism for alkali ions in TB structures and present a qualitative descriptor to predict the local volume change, which provides a way for faster screening and discovery of novel ZS battery materials.
{"title":"First-principles study of strain behavior in iron-based fluorides of tungsten bronze type as cathode materials for alkali-ion batteries","authors":"A. F. Baumann, D. Mutter, D. F. Urban, C. Elsässer","doi":"10.1103/physrevmaterials.8.095401","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.095401","url":null,"abstract":"Mechanical stresses and strains in the microstructure of cathode materials evolving during charge/discharge cycles can reduce the long-term stability of intercalation type alkali-metal-ion batteries. In this context, crystalline compounds exhibiting zero-strain (ZS) behavior are of particular interest. Near-ZS sodiation was experimentally measured in the tetragonal tungsten bronze (TTB) type compound <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Na</mi><mi>x</mi></msub><msub><mi>FeF</mi><mn>3</mn></msub></mrow></math>. Using a first-principles method based on density functional theory, we investigate the potential of iron-based fluoride compounds with tungsten bronze (TB) structures as ZS cathode materials. Simulations were conducted to study the intercalation of the alkali metal ions <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi>Li</mi><mo>+</mo></msup><mo>,</mo><mo> </mo><msup><mi>Na</mi><mo>+</mo></msup></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi mathvariant=\"normal\">K</mi><mo>+</mo></msup></math> into the TTB and two related TB structures of the cubic perovskite and hexagonal types. We describe compensating local volume effects that can explain the experimentally measured low volume change of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Na</mi><mi>x</mi></msub><msub><mi>FeF</mi><mn>3</mn></msub></mrow></math>. We discuss the structural and chemical prerequisites of the host lattice for a ZS insertion mechanism for alkali ions in TB structures and present a qualitative descriptor to predict the local volume change, which provides a way for faster screening and discovery of novel ZS battery materials.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-13DOI: 10.1103/physrevmaterials.8.093402
Daniel L. Coelho, Duncan Burns, Emily Wilson, Nikolas Provatas
In a recent class of phase field crystal (PFC) models, the density order parameter is coupled to powers of its mean field. This effectively introduces a phenomenology of higher-order direct correlation functions acting on long wavelengths, which is required for modeling solid-liquid-vapor systems. The present work generalizes these models by incorporating, into a single-field theory, higher-order direct correlations, systematically constructed in reciprocal space to operate across long and short wavelengths. The correlation kernels introduced are also readily adaptable to describe distinct crystal structures. We examine the three-phase equilibrium properties and phase diagrams of the proposed model, and reproduce parts of the aluminum phase diagram as an example of its versatile parametrization. We assess the dynamics of the model, showing that it allows robust control of the interface energy between the vapor and condensed phases (liquid and solid). We also examine the dynamics of solid-vapor interfaces over a wide range of parameters and find that dynamical artifacts reported in previous PFC models do not occur in the present formalism. Additionally, we demonstrate the capacity of the proposed formalism for computing complex microstructures and defects such as dislocations, grain boundaries, and voids in solid-liquid-vapor systems, all of which are expected to be crucial for investigating rapid solidification processes.
{"title":"Generalizing the structural phase field crystal approach for modeling solid-liquid-vapor phase transformations in pure materials","authors":"Daniel L. Coelho, Duncan Burns, Emily Wilson, Nikolas Provatas","doi":"10.1103/physrevmaterials.8.093402","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093402","url":null,"abstract":"In a recent class of phase field crystal (PFC) models, the density order parameter is coupled to powers of its mean field. This effectively introduces a phenomenology of higher-order direct correlation functions acting on long wavelengths, which is required for modeling solid-liquid-vapor systems. The present work generalizes these models by incorporating, into a single-field theory, higher-order direct correlations, systematically constructed in reciprocal space to operate across long <i>and</i> short wavelengths. The correlation kernels introduced are also readily adaptable to describe distinct crystal structures. We examine the three-phase equilibrium properties and phase diagrams of the proposed model, and reproduce parts of the aluminum phase diagram as an example of its versatile parametrization. We assess the dynamics of the model, showing that it allows robust control of the interface energy between the vapor and condensed phases (liquid and solid). We also examine the dynamics of solid-vapor interfaces over a wide range of parameters and find that dynamical artifacts reported in previous PFC models do not occur in the present formalism. Additionally, we demonstrate the capacity of the proposed formalism for computing complex microstructures and defects such as dislocations, grain boundaries, and voids in solid-liquid-vapor systems, all of which are expected to be crucial for investigating rapid solidification processes.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-13DOI: 10.1103/physrevmaterials.8.094406
Dylan Windsor, Haixuan Xu
Interactions between polarons and oxygen vacancies in oxides, which cause them to modify one another's physical properties, are highly important for applications such as photovoltaics and ferroelectrics. While the difficulty in modeling polarons using density functional theory (DFT) calculations has been alleviated by the recent development of various techniques, including, e.g., the Hubbard-U parameter and finite-size corrections, the underlying physics of polaron interactions with defects remains unknown. Here, we demonstrate that the polaron-vacancy complexes in have a preferred orbital configuration, different from the orbital configuration of the bulk polaron, by exploring multiple nearby local minima using . To address the issue of polaron property dependence on the Hubbard-U value, we determine the U value via enforcement of piecewise linearity, and we employ finite-size corrections. Three local minima with different electronic configurations are found by varying the initial conditions: (i) a polaron trapped in a orbital on the first-nearest-neighbor Ti-ion of the oxygen vacancy ( complex), (ii) a polaron trapped in a orbital at the same position ( complex), and (iii) electrons delocalized across several nearby sites and both spin channels, resulting in a semilocalized state. We find that the complex is the most energetically favorable state, revealing a change in the orbital of the polaron when trapped by an oxygen vacancy, since the bulk polaron is found to be in a orbital. Furthermore, we demonstrate that great care must be taken to find the correct physical picture with , since a small change in the initial conditions results in finding different local minima.
{"title":"Treating interactions between polarons and oxygen vacancies in perovskite oxides","authors":"Dylan Windsor, Haixuan Xu","doi":"10.1103/physrevmaterials.8.094406","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094406","url":null,"abstract":"Interactions between polarons and oxygen vacancies in oxides, which cause them to modify one another's physical properties, are highly important for applications such as photovoltaics and ferroelectrics. While the difficulty in modeling polarons using density functional theory (DFT) calculations has been alleviated by the recent development of various techniques, including, e.g., the Hubbard-U parameter and finite-size corrections, the underlying physics of polaron interactions with defects remains unknown. Here, we demonstrate that the polaron-vacancy complexes in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>PbTi</mi><msub><mi mathvariant=\"normal\">O</mi><mn>3</mn></msub></mrow></math> have a preferred orbital configuration, different from the orbital configuration of the bulk polaron, by exploring multiple nearby local minima using <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>DFT</mi><mo>+</mo><mi mathvariant=\"normal\">U</mi></mrow></math>. To address the issue of polaron property dependence on the Hubbard-U value, we determine the U value via enforcement of piecewise linearity, and we employ finite-size corrections. Three local minima with different electronic configurations are found by varying the initial conditions: (i) a polaron trapped in a <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mrow><mi>Ti</mi><mtext>−</mtext></mrow><mn>3</mn><msub><mi>d</mi><mrow><mi>e</mi><mi>g</mi></mrow></msub></mrow></math> orbital on the first-nearest-neighbor Ti-ion of the oxygen vacancy (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>e</mi><mi>g</mi></mrow></math> complex), (ii) a polaron trapped in a <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mrow><mi>Ti</mi><mtext>−</mtext></mrow><mn>3</mn><msub><mi>d</mi><mrow><mi>t</mi><mn>2</mn><mi>g</mi></mrow></msub></mrow></math> orbital at the same position (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>t</mi><mn>2</mn><mi>g</mi></mrow></math> complex), and (iii) electrons delocalized across several nearby sites and both spin channels, resulting in a semilocalized state. We find that the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>e</mi><mi>g</mi></mrow></math> complex is the most energetically favorable state, revealing a change in the orbital of the polaron when trapped by an oxygen vacancy, since the bulk polaron is found to be in a <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>t</mi><mn>2</mn><mi>g</mi></mrow></math> orbital. Furthermore, we demonstrate that great care must be taken to find the correct physical picture with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>DFT</mi><mo>+</mo><mi mathvariant=\"normal\">U</mi></mrow></math>, since a small change in the initial conditions results in finding different local minima.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-13DOI: 10.1103/physrevmaterials.8.095001
Jyotish Patidar, Kerstin Thorwarth, Thorsten Schmitz-Kempen, Roland Kessels, Sebastian Siol
With the integration of 5G in day-to-day devices and the foreseeable 6G revolution, demand for advanced radio frequency (RF) microelectromechanical systems (MEMS) is growing. Aluminum scandium nitride (AlScN) has emerged as the material of choice for many of those applications due to its superior piezoelectric and electromechanical properties compared to aluminum nitride (AlN). However, synthesizing high-quality, textured AlScN thin films is challenging. Alloying of Sc in AlN induces structural frustration leading to strain, defects, disoriented grains, and disrupted crystal symmetry during growth. Higher deposition temperatures, while improving crystalline quality, risk undesirable phase precipitation and limit industrial sustainability. In addition, future MEMS technologies also demand conformal and textured coatings over diverse topographies. Addressing these challenges collectively requires new and innovative synthesis approaches. In this study, we investigate the feasibility of ionized physical vapor deposition to deposit highly oriented AlScN films with minimal defects at lower temperatures. To this end, we employ combinations of different deposition approaches, such as metal-ion synchronized (MIS) high-power impulse magnetron sputtering (HiPIMS). Leveraging the high ionization rates of HiPIMS and optimally timed substrate bias potentials, we selectively bombard the growing film with Al and/or Sc ions to enhance the adatom mobility at low temperatures while simultaneously providing the ability to tune stress and coat complex structures conformally. The nonequilibrium solubility of Sc in wurtzite AlN under different conditions is investigated using a combinatorial deposition approach. Promising candidates with Sc composition are isolated and characterized for crystallinity and residual stress. Disoriented grains, a significant issue in growing AlScN films, are observed through atomic force microscopy and found to be completely removed by substrate rotation and application of substrate biasing. The measured piezoelectric response of the films with approximately 20% Sc concentration ranges from 6.3 to 8.8 , in line with density functional theory predictions and experimentally reported values for films deposited in a production tool with coplanar geometry. At the same time, MIS-HiPIMS-deposited films offer unique properties and flexibility to tune their stress state and structural properties, thus presenting exciting opportunities for the fabrication of advanced RF filters and next-generation MEMS devices.
{"title":"Deposition of highly crystalline AlScN thin films using synchronized high-power impulse magnetron sputtering: From combinatorial screening to piezoelectric devices","authors":"Jyotish Patidar, Kerstin Thorwarth, Thorsten Schmitz-Kempen, Roland Kessels, Sebastian Siol","doi":"10.1103/physrevmaterials.8.095001","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.095001","url":null,"abstract":"With the integration of 5G in day-to-day devices and the foreseeable 6G revolution, demand for advanced radio frequency (RF) microelectromechanical systems (MEMS) is growing. Aluminum scandium nitride (AlScN) has emerged as the material of choice for many of those applications due to its superior piezoelectric and electromechanical properties compared to aluminum nitride (AlN). However, synthesizing high-quality, textured AlScN thin films is challenging. Alloying of Sc in AlN induces structural frustration leading to strain, defects, disoriented grains, and disrupted crystal symmetry during growth. Higher deposition temperatures, while improving crystalline quality, risk undesirable phase precipitation and limit industrial sustainability. In addition, future MEMS technologies also demand conformal and textured coatings over diverse topographies. Addressing these challenges collectively requires new and innovative synthesis approaches. In this study, we investigate the feasibility of ionized physical vapor deposition to deposit highly oriented AlScN films with minimal defects at lower temperatures. To this end, we employ combinations of different deposition approaches, such as metal-ion synchronized (MIS) high-power impulse magnetron sputtering (HiPIMS). Leveraging the high ionization rates of HiPIMS and optimally timed substrate bias potentials, we selectively bombard the growing film with Al and/or Sc ions to enhance the adatom mobility at low temperatures while simultaneously providing the ability to tune stress and coat complex structures conformally. The nonequilibrium solubility of Sc in wurtzite AlN under different conditions is investigated using a combinatorial deposition approach. Promising candidates with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>∼</mo><mn>20</mn><mo>%</mo></mrow></math> Sc composition are isolated and characterized for crystallinity and residual stress. Disoriented grains, a significant issue in growing AlScN films, are observed through atomic force microscopy and found to be completely removed by substrate rotation and application of substrate biasing. The measured piezoelectric response of the films with approximately 20% Sc concentration ranges from 6.3 to 8.8 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>pm</mi><mo>/</mo><mi mathvariant=\"normal\">V</mi></mrow></math>, in line with density functional theory predictions and experimentally reported values for films deposited in a production tool with coplanar geometry. At the same time, MIS-HiPIMS-deposited films offer unique properties and flexibility to tune their stress state and structural properties, thus presenting exciting opportunities for the fabrication of advanced RF filters and next-generation MEMS devices.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1103/physrevmaterials.8.093605
Sena Hoshino, Shuji Oi, Yu Ogura, Tatsuya Yokoi, Yan Li, Atsutomo Nakamura, Katsuyuki Matsunaga
It was experimentally reported that light illumination leads to reduced deformation stresses in some III-V compound semiconductors such as GaP. This phenomenon is known as the negative photoplastic effect, which is expected to originate from interactions between photoexcited carriers and glide dislocations. To clarify its physical origin at the atomic and electronic levels, density-functional-theory calculations were performed for Shockley partial dislocations in GaP. In the absence of excess carriers, both Ga and P cores of the partial dislocations were found to have reconstructed structures that are energetically most stable. This can be understood by the fact that dangling-bond-like states at undercoordinated atoms of the dislocation cores are removed by core reconstruction. In the presence of excess carriers that would be formed by light illumination, the reconstructed Ga and P cores were able to trap excess holes and electrons, respectively, and were subsequently transformed to unreconstructed structures. It was also found that the unreconstructed structures due to excess carriers tend to have smaller potential barrier heights for dislocation glide, as compared to the pristine reconstructed structures without any excess carriers. This is in good agreement with the increased dislocation mobility in GaP under external light illumination that has been experimentally reported.
据实验报告，光照会导致某些 III-V 族化合物半导体（如 GaP）的变形应力减小。这种现象被称为负光塑性效应，预计源于光激发载流子与滑行位错之间的相互作用。为了在原子和电子水平上阐明其物理起源，我们对 GaP 中的肖克利 30∘ 部分位错进行了密度函数理论计算。结果发现，在没有过量载流子的情况下，部分位错的 Ga 核和 P 核都具有能量最稳定的重构结构。这可以从差排核心中配位不足的原子上的类悬空键态被核心重构所消除这一事实中得到解释。在光照下会形成过剩载流子的情况下，重构的镓核和铂核能够分别捕获过剩的空穴和电子，随后转变为非重构结构。研究还发现，与没有过剩载流子的原始重构结构相比，过剩载流子导致的非重构结构往往具有较小的位错滑行势垒高度。这与实验报告的 GaP 在外部光照下位错迁移率增加的现象十分吻合。
{"title":"Atomic-structure changes of 30∘ partial-dislocation cores due to excess carriers in GaP","authors":"Sena Hoshino, Shuji Oi, Yu Ogura, Tatsuya Yokoi, Yan Li, Atsutomo Nakamura, Katsuyuki Matsunaga","doi":"10.1103/physrevmaterials.8.093605","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093605","url":null,"abstract":"It was experimentally reported that light illumination leads to reduced deformation stresses in some III-V compound semiconductors such as GaP. This phenomenon is known as the negative photoplastic effect, which is expected to originate from interactions between photoexcited carriers and glide dislocations. To clarify its physical origin at the atomic and electronic levels, density-functional-theory calculations were performed for Shockley <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>30</mn><mo>∘</mo></msup></math> partial dislocations in GaP. In the absence of excess carriers, both Ga and P cores of the partial dislocations were found to have reconstructed structures that are energetically most stable. This can be understood by the fact that dangling-bond-like states at undercoordinated atoms of the dislocation cores are removed by core reconstruction. In the presence of excess carriers that would be formed by light illumination, the reconstructed Ga and P cores were able to trap excess holes and electrons, respectively, and were subsequently transformed to unreconstructed structures. It was also found that the unreconstructed structures due to excess carriers tend to have smaller potential barrier heights for dislocation glide, as compared to the pristine reconstructed structures without any excess carriers. This is in good agreement with the increased dislocation mobility in GaP under external light illumination that has been experimentally reported.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Strain in materials changes their electronic structure, and the strain response realizes rich material properties and devices. Superconductivity under hydrostatic pressure and epitaxial strain suggests significant response to an external variable strain in a single sample, but this has not yet been demonstrated because the strain is usually a fixed parameter after sample fabrication. films were fabricated on flexible metal substrates, and bending strain was applied to them to observe the critical temperature and resistivity variation induced by strain. The compressive bending strain of −0.005 increased the from 23.4 to 27.3 K. The magnitude of the change by the bending strain is independent of the doping level and initial epitaxial strain. Furthermore, the irreversibility temperature was also improved by the compressive bending, and reasonable variation with respect to the reversible strain was observed. b initio density functional calculation for the mother compound clarified that the low-energy electronic structures are sensitive to the bending strain. While the carriers (holes) are preferentially injected into the in-plane orbitals of the plane under the compressive strain, the tensile strain leads to the carrier injection into the perpendicular orbitals which is unfavorable to the superconductivity. The strain-sensitive high- superconductor under the external strain highlights a new aspect for cuprate superconductors, which opens monitoring of the stress situation in the cryogenic systems such as superconducting magnet and liquid hydrogen container.
材料中的应变会改变其电子结构，应变响应会实现丰富的材料特性和器件。静水压力和外延应变下的超导性表明，单个样品对外部可变应变有显著的响应，但由于应变通常是样品制作后的固定参数，这一点尚未得到证实。(在柔性金属基底上制作了 (La,Sr)2CuO4薄膜，并对其施加了弯曲应变，以观察应变引起的临界温度（Tc）和电阻率变化。-0.005的压缩弯曲应变将临界温度从23.4 K提高到27.3 K。弯曲应变引起的临界温度变化幅度与掺杂水平和初始外延应变无关。此外，压缩弯曲还提高了不可逆温度，并观察到 Tc 随可逆应变的合理变化。对母体化合物 La2CuO4 的 Ab initio 密度泛函计算表明，低能电子结构对弯曲应变很敏感。在压缩应变下，载流子（空穴）优先注入到 CuO2 平面的面内轨道中，而拉伸应变则导致载流子注入到垂直轨道中，不利于超导。外部应变下的应变敏感型高锝超导体凸显了杯状超导体的一个新方面，从而开启了对超导磁体和液氢容器等低温系统中应力情况的监测。
{"title":"Tc and resistivity variation induced by external bending strain in flexible film of strain-sensitive (La,Sr)2CuO4","authors":"Tomoya Horide, Tomoaki Maekawa, Tatsuro Aikawa, Takanori Kitamura, Kazuma Nakamura","doi":"10.1103/physrevmaterials.8.094802","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094802","url":null,"abstract":"Strain in materials changes their electronic structure, and the strain response realizes rich material properties and devices. Superconductivity under hydrostatic pressure and epitaxial strain suggests significant response to an external variable strain in a single sample, but this has not yet been demonstrated because the strain is usually a fixed parameter after sample fabrication. <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mo>(</mo><mrow><mi>La</mi><mo>,</mo><mi>Sr</mi></mrow><mo>)</mo></mrow><mn>2</mn></msub><mi>Cu</mi><msub><mi mathvariant=\"normal\">O</mi><mn>4</mn></msub></mrow></math> films were fabricated on flexible metal substrates, and bending strain was applied to them to observe the critical temperature <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub><mo>)</mo></mrow></math> and resistivity variation induced by strain. The compressive bending strain of −0.005 increased the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> from 23.4 to 27.3 K. The magnitude of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> change by the bending strain is independent of the doping level and initial epitaxial strain. Furthermore, the irreversibility temperature was also improved by the compressive bending, and reasonable <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> variation with respect to the reversible strain was observed. <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>A</mi></mrow></math><i>b initio</i> density functional calculation for the mother compound <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">L</mi><msub><mi mathvariant=\"normal\">a</mi><mn>2</mn></msub><mi>Cu</mi><msub><mi mathvariant=\"normal\">O</mi><mn>4</mn></msub></mrow></math> clarified that the low-energy electronic structures are sensitive to the bending strain. While the carriers (holes) are preferentially injected into the in-plane orbitals of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Cu</mi><msub><mi mathvariant=\"normal\">O</mi><mn>2</mn></msub></mrow></math> plane under the compressive strain, the tensile strain leads to the carrier injection into the perpendicular orbitals which is unfavorable to the superconductivity. The strain-sensitive high-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> superconductor under the external strain highlights a new aspect for cuprate superconductors, which opens monitoring of the stress situation in the cryogenic systems such as superconducting magnet and liquid hydrogen container.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1103/physrevmaterials.8.093801
Dereje Bekele Tekliye, Gopalakrishnan Sai Gautam
Accurate predictions of material properties within the chemical space of transition metal fluorides (TMFs), using computational frameworks such as density functional theory (DFT), is important for advancing several technological applications. The state-of-the-art semilocal exchange-correlation functionals within DFT include the strongly constrained and appropriately normed (SCAN) and the restored regularized SCAN (<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mrow><mi mathvariant="normal">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math>), both of which are meta generalized gradient approximation (metaGGA) functionals. Given their semilocal nature, both SCAN and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mrow><mi mathvariant="normal">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math> are susceptible to self-interaction errors (SIEs) while modeling highly correlated <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>d</mi></math> electrons of transition metals. Hence, in this work, we evaluate the accuracy of both SCAN and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mrow><mi mathvariant="normal">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math> functionals in estimating several properties of TMFs, including redox enthalpies, lattice geometries, on-site magnetic moments, and band gaps. Specifically, we consider binary fluorides of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. We observe both SCAN and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mrow><mi mathvariant="normal">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math> exhibit poor accuracy in estimating fluorination enthalpies among TMFs, which can be primarily attributed to SIEs among the <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>d</mi></math> electrons, given both functionals bind <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="normal">F</mi><mn>2</mn></msub></math> accurately. Thus, we derive optimal Hubbard <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>U</mi></mrow></math> corrections for both functionals based on experimental fluorination (or oxidation) enthalpies within binary TMFs. Note that our attempts at using the linear response theory to derive <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>U</mi></mrow></math> corrections yielded unphysical values for V, Fe, and Ni fluorides. While adding the fluorination-enthalpy-derived <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>U</mi></mrow></math> corrections to the metaGGA functionals does not significantly affect the lattice volumes and on-site magnetic moments (and in turn, the accuracy of these property estimations versus experiments), it does cause a significant increase in calculated band gaps. Note that the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>U</mi></mrow></math>-corrected band gaps in several fluorides deviate to a lesser extent from band gaps calc
利用密度泛函理论（DFT）等计算框架对过渡金属氟化物（TMFs）化学空间内的材料特性进行精确预测，对于推动多项技术应用非常重要。DFT 中最先进的半局部交换相关函数包括强约束和适当规范化（SCAN）和恢复正则化 SCAN（r2SCAN），两者都是元广义梯度近似（metaGGA）函数。鉴于其半局部性质，SCAN 和 r2SCAN 在模拟过渡金属高度相关的 d 电子时都容易受到自相互作用误差（SIE）的影响。因此，在这项工作中，我们评估了 SCAN 和 r2SCAN 函数在估算 TMFs 的几种性质（包括氧化还原焓、晶格几何形状、现场磁矩和带隙）时的准确性。具体来说，我们考虑了 Ti、V、Cr、Mn、Fe、Co、Ni 和 Cu 的二元氟化物。我们发现 SCAN 和 r2SCAN 在估算 TMF 的氟化焓时都表现出了较差的准确性，这主要归因于 d 电子间的 SIEs，因为这两种函数都能准确地结合 F2。因此，我们根据二元 TMF 中的实验氟化（或氧化）焓，推导出这两种函数的最佳哈伯德 U 修正值。需要注意的是，我们尝试使用线性响应理论来推导 U 修正值，结果发现 V、Fe 和 Ni 氟化物的 U 修正值是非物理的。虽然在元 GGA 函数中加入氟化焓衍生 U 修正并不会显著影响晶格体积和现场磁矩（进而影响这些属性估计与实验对比的准确性），但它确实会导致计算带隙的显著增加。请注意，与非 U 修正函数相比，几种氟化物的 U 修正带隙与混合函数计算带隙的偏差较小。此外，我们还计算了锰、铁、钴和镍氟化物中 Na 的平均闰化电压，以及 Na-V-F、Na-Cr-F、Na-Mn-F 和 Na-Fe-F 三元化合物的稳定性，作为最佳 U 值的可转移性检验。总之，我们建议采用哈伯德 U 修正来改进其他 TMF 中氧化还原焓的预测。最后，我们的研究应能提高基于 DFT 的筛选研究的准确性，从而发现新型 TMF，并将其应用于各种领域，包括储能、催化和磁性器件。
{"title":"Accuracy of metaGGA functionals in describing transition metal fluorides","authors":"Dereje Bekele Tekliye, Gopalakrishnan Sai Gautam","doi":"10.1103/physrevmaterials.8.093801","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093801","url":null,"abstract":"Accurate predictions of material properties within the chemical space of transition metal fluorides (TMFs), using computational frameworks such as density functional theory (DFT), is important for advancing several technological applications. The state-of-the-art semilocal exchange-correlation functionals within DFT include the strongly constrained and appropriately normed (SCAN) and the restored regularized SCAN (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mrow><mi mathvariant=\"normal\">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math>), both of which are meta generalized gradient approximation (metaGGA) functionals. Given their semilocal nature, both SCAN and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mrow><mi mathvariant=\"normal\">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math> are susceptible to self-interaction errors (SIEs) while modeling highly correlated <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>d</mi></math> electrons of transition metals. Hence, in this work, we evaluate the accuracy of both SCAN and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mrow><mi mathvariant=\"normal\">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math> functionals in estimating several properties of TMFs, including redox enthalpies, lattice geometries, on-site magnetic moments, and band gaps. Specifically, we consider binary fluorides of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. We observe both SCAN and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mrow><mi mathvariant=\"normal\">r</mi></mrow><mn>2</mn></msup><mi>SCAN</mi></mrow></math> exhibit poor accuracy in estimating fluorination enthalpies among TMFs, which can be primarily attributed to SIEs among the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>d</mi></math> electrons, given both functionals bind <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">F</mi><mn>2</mn></msub></math> accurately. Thus, we derive optimal Hubbard <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>U</mi></mrow></math> corrections for both functionals based on experimental fluorination (or oxidation) enthalpies within binary TMFs. Note that our attempts at using the linear response theory to derive <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>U</mi></mrow></math> corrections yielded unphysical values for V, Fe, and Ni fluorides. While adding the fluorination-enthalpy-derived <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>U</mi></mrow></math> corrections to the metaGGA functionals does not significantly affect the lattice volumes and on-site magnetic moments (and in turn, the accuracy of these property estimations versus experiments), it does cause a significant increase in calculated band gaps. Note that the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>U</mi></mrow></math>-corrected band gaps in several fluorides deviate to a lesser extent from band gaps calc","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1103/physrevmaterials.8.l091402
Nikhilesh Maity, Ravi Kashikar, S. Lisenkov, I. Ponomareva
Spin splitting, or removal of spin degeneracy in the electronic energy band/level, is often a measure of spin-orbit coupling strength and a way to manipulate spin degrees of freedom. We use first-principles simulations to predict giant spin splitting in methylhydrazinium lead halide ( = Br and Cl) hybrid organic-inorganic perovskites. The values can reach up to 408.0 meV at zero Kelvin and 281.6 meV at room temperature. The origin of the effect is traced to the large distortion of framework, driven primarily by Pb ions in the ferroelectric mode. The Pb displacements consist of a combination of polar and antipolar arrangements and result in up to 39.2 meV/atom enhancement of the spin-orbit coupling energy in the polar phase of the materials. The spin-orbit coupling gives origin to persistent spin textures in , which are desirable for applications in spintronics and quantum computing. Our findings reveal an additional functionality for hybrid organic-inorganic perovskite and open a way for the design of more materials with giant spin splitting.
{"title":"Giant spin splitting and its origin in methylhydrazinium lead halide perovskites","authors":"Nikhilesh Maity, Ravi Kashikar, S. Lisenkov, I. Ponomareva","doi":"10.1103/physrevmaterials.8.l091402","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.l091402","url":null,"abstract":"Spin splitting, or removal of spin degeneracy in the electronic energy band/level, is often a measure of spin-orbit coupling strength and a way to manipulate spin degrees of freedom. We use first-principles simulations to predict giant spin splitting in methylhydrazinium lead halide (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MHyPbX</mi><mn>3</mn></msub><mo>,</mo><mo> </mo><mrow><mi>MHy</mi><mo>=</mo><msub><mi>CH</mi><mn>3</mn></msub><msub><mi>NH</mi><mn>2</mn></msub><msub><mi>NH</mi><mn>2</mn></msub></mrow><mo>,</mo><mo> </mo><mrow><mi>X</mi></mrow></math> = Br and Cl) hybrid organic-inorganic perovskites. The values can reach up to 408.0 meV at zero Kelvin and 281.6 meV at room temperature. The origin of the effect is traced to the large distortion of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>PbX</mi><mn>3</mn></msub></math> framework, driven primarily by Pb ions in the ferroelectric <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi mathvariant=\"normal\">Γ</mi><mrow><mn>3</mn><mo>−</mo></mrow></msup></math> mode. The Pb displacements consist of a combination of polar and antipolar arrangements and result in up to 39.2 meV/atom enhancement of the spin-orbit coupling energy in the polar phase of the materials. The spin-orbit coupling gives origin to persistent spin textures in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MHyPbX</mi><mn>3</mn></msub></math>, which are desirable for applications in spintronics and quantum computing. Our findings reveal an additional functionality for hybrid organic-inorganic perovskite and open a way for the design of more materials with giant spin splitting.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1103/physrevmaterials.8.093604
Aleksei Egorov, Antoine Kraych, Matous Mrovec, Ralf Drautz, Thomas Hammerschmidt
We elucidated the core structure of screw dislocations in ordered B2 FeCo using a recent magnetic bond-order potential (BOP) [Egorov et al., Phys. Rev. Mater.7, 044403 (2023)]. We corroborated that dislocations in B2 FeCo exist in pairs separated by antiphase boundaries. The equilibrium separation is about 50 Å, which demands large-scale atomistic simulations—inaccessible for density functional theory but attainable with BOP. We performed atomistic simulations of these separated dislocations with BOP and predicted that they reside in degenerate core structures. Additionally, dislocations induce changes in the local electronic structure and magnetic moments.
{"title":"Core structure of dislocations in ordered ferromagnetic FeCo","authors":"Aleksei Egorov, Antoine Kraych, Matous Mrovec, Ralf Drautz, Thomas Hammerschmidt","doi":"10.1103/physrevmaterials.8.093604","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093604","url":null,"abstract":"We elucidated the core structure of screw dislocations in ordered B2 FeCo using a recent magnetic bond-order potential (BOP) [Egorov <i>et al.</i>, <span>Phys. Rev. Mater.</span> <b>7</b>, 044403 (2023)]. We corroborated that dislocations in B2 FeCo exist in pairs separated by antiphase boundaries. The equilibrium separation is about 50 Å, which demands large-scale atomistic simulations—inaccessible for density functional theory but attainable with BOP. We performed atomistic simulations of these separated dislocations with BOP and predicted that they reside in degenerate core structures. Additionally, dislocations induce changes in the local electronic structure and magnetic moments.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1103/physrevmaterials.8.094602
Darshana Wickramaratne, Mackenzie Siford, Md Shafiqul Islam Mollik, John L. Lyons, M. E. Zvanut
We use photo-electron paramagnetic resonance (EPR) measurements and first-principles calculations to identify and explain the properties of carbon in AlN. We present clear evidence for carbon substitution on the nitrogen site (). We also clarify the origin of a widely observed EPR spectra in AlN that, although often attributed to a deep donor defect, we demonstrate is surprisingly due to . Finally, we show the presence of is consistent with the absorption spectra at 4.7 eV observed in AlN.
{"title":"Direct evidence for carbon incorporation on the nitrogen site in AlN","authors":"Darshana Wickramaratne, Mackenzie Siford, Md Shafiqul Islam Mollik, John L. Lyons, M. E. Zvanut","doi":"10.1103/physrevmaterials.8.094602","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094602","url":null,"abstract":"We use photo-electron paramagnetic resonance (EPR) measurements and first-principles calculations to identify and explain the properties of carbon in AlN. We present clear evidence for carbon substitution on the nitrogen site (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">C</mi><mi mathvariant=\"normal\">N</mi></msub></math>). We also clarify the origin of a widely observed EPR spectra in AlN that, although often attributed to a deep donor defect, we demonstrate is surprisingly due to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">C</mi><mi mathvariant=\"normal\">N</mi></msub></math>. Finally, we show the presence of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">C</mi><mi mathvariant=\"normal\">N</mi></msub></math> is consistent with the absorption spectra at 4.7 eV observed in AlN.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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