Pub Date : 2024-09-19DOI: 10.1103/physrevmaterials.8.094002
Shota Ono, Ravinder Pawar
The 2H, 1T, and their distorted structures are known as prototype structures of monolayers. Here, we study a puckered (PCK) structure that is truncated from the (110) surface of fluorite-type materials. 53 fluorite-type materials are investigated based on first-principles approach. The formation energy calculations indicate that seven systems form the PCK structure in the monolayer limit, while other systems form either 1T, 2H, or distorted 1T structures. The PCK structures of and exhibit negative Poisson's ratio (NPR) in the out-of-plane direction. We explain the NPR by an analytical model assuming a constant interatomic distance under the in-plane strain. In addition, we demonstrate that the appearance of NPR is correlated with non-ionic character of the system, which is based on the surface energy calculations and the Born effective charge analyses. We also find that in the PCK structure is highly distorted.
{"title":"Fluorite-type materials in the monolayer limit","authors":"Shota Ono, Ravinder Pawar","doi":"10.1103/physrevmaterials.8.094002","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094002","url":null,"abstract":"The 2H, 1T, and their distorted structures are known as prototype structures of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>A</mi><msub><mi>B</mi><mn>2</mn></msub></mrow></math> monolayers. Here, we study a puckered (PCK) structure that is truncated from the (110) surface of fluorite-type materials. 53 fluorite-type materials are investigated based on first-principles approach. The formation energy calculations indicate that seven systems form the PCK structure in the monolayer limit, while other systems form either 1T, 2H, or distorted 1T structures. The PCK structures of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>PbF</mi><mn>2</mn></msub></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Ga</mi><mn>2</mn></msub><mi>Au</mi></mrow></math> exhibit negative Poisson's ratio (NPR) in the out-of-plane direction. We explain the NPR by an analytical model assuming a constant interatomic distance under the in-plane strain. In addition, we demonstrate that the appearance of NPR is correlated with non-ionic character of the system, which is based on the surface energy calculations and the Born effective charge analyses. We also find that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>PRh</mi><mn>2</mn></msub></math> in the PCK structure is highly distorted.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266609","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 : 2024-09-19DOI: 10.1103/physrevmaterials.8.094202
Jian Yuan, Xianbiao Shi, Hong Du, Wei Xia, Xia Wang, Jinguang Cheng, Baotian Wang, Ruidan Zhong, Shihao Zhang, Yanfeng Guo
The correlation between magnetism and nontrivial topological band structure serves as a unique venue for discovering exotic topological properties. Combining magnetotransport measurements and first-principles calculations, we unveil herein that the hexagonal EuCuP holds a topologically trivial state in the paramagnetic structure, while strong magnetization dependent anisotropic topological states in the spin-polarization structures. Specifically, it hosts a trivial topological state in the in-plane spin-polarization structure, while a Weyl semimetal state in the out-of-plane spin-polarization structure. Our scaling analysis suggests that the intrinsic Berry curvature in the spin-polarization structures can account for the observed large anisotropic anomalous Hall effect. First-principles calculations show that the magnetization and the spin-orbit coupling simultaneously play essential roles for the appearance of the four pairs of Weyl points in the out-of-plane spin-polarization structure. Our work therefore establishes in EuCuP the intimate relation between magnetism and the nontrivial topological states, which would be instructive for future study on this key issue of topological physics.
{"title":"Magnetization dependent anisotropic topological properties in EuCuP","authors":"Jian Yuan, Xianbiao Shi, Hong Du, Wei Xia, Xia Wang, Jinguang Cheng, Baotian Wang, Ruidan Zhong, Shihao Zhang, Yanfeng Guo","doi":"10.1103/physrevmaterials.8.094202","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094202","url":null,"abstract":"The correlation between magnetism and nontrivial topological band structure serves as a unique venue for discovering exotic topological properties. Combining magnetotransport measurements and first-principles calculations, we unveil herein that the hexagonal EuCuP holds a topologically trivial state in the paramagnetic structure, while strong magnetization dependent anisotropic topological states in the spin-polarization structures. Specifically, it hosts a trivial topological state in the in-plane spin-polarization structure, while a Weyl semimetal state in the out-of-plane spin-polarization structure. Our scaling analysis suggests that the intrinsic Berry curvature in the spin-polarization structures can account for the observed large anisotropic anomalous Hall effect. First-principles calculations show that the magnetization and the spin-orbit coupling simultaneously play essential roles for the appearance of the four pairs of Weyl points in the out-of-plane spin-polarization structure. Our work therefore establishes in EuCuP the intimate relation between magnetism and the nontrivial topological states, which would be instructive for future study on this key issue of topological physics.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266455","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 : 2024-09-19DOI: 10.1103/physrevmaterials.8.093403
S. Kiana Naghibzadeh, Zipeng Xu, David Kinderlehrer, Robert Suter, Kaushik Dayal, Gregory S. Rohrer
A threshold dynamics model of grain growth that accounts for the anisotropy in the grain boundary energy has been used to simulate experimentally observed grain growth of polycrystalline Ni. The simulation reproduces several aspects of the observed microstructural evolution that are not found in the results of simulations assuming isotropic properties. For example, the relative areas of the lowest-energy twin boundaries increase as the grains grow and the average grain boundary energy decreases with grain growth. This decrease in energy occurs because the population of higher-energy grain boundaries decreases while the population of lower-energy boundaries increases as the total grain boundary area decreases. This phenomenon emerges from the assumption of anisotropic grain boundary energies without modification of the energy minimizing algorithm. These findings are consistent with the observation that, in addition to the decrease in grain boundary area, additional energy is dissipated during grain growth by a decrease in the average grain boundary energy.
{"title":"Impact of grain boundary energy anisotropy on grain growth","authors":"S. Kiana Naghibzadeh, Zipeng Xu, David Kinderlehrer, Robert Suter, Kaushik Dayal, Gregory S. Rohrer","doi":"10.1103/physrevmaterials.8.093403","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093403","url":null,"abstract":"A threshold dynamics model of grain growth that accounts for the anisotropy in the grain boundary energy has been used to simulate experimentally observed grain growth of polycrystalline Ni. The simulation reproduces several aspects of the observed microstructural evolution that are not found in the results of simulations assuming isotropic properties. For example, the relative areas of the lowest-energy twin boundaries increase as the grains grow and the average grain boundary energy decreases with grain growth. This decrease in energy occurs because the population of higher-energy grain boundaries decreases while the population of lower-energy boundaries increases as the total grain boundary area decreases. This phenomenon emerges from the assumption of anisotropic grain boundary energies without modification of the energy minimizing algorithm. These findings are consistent with the observation that, in addition to the decrease in grain boundary area, additional energy is dissipated during grain growth by a decrease in the average grain boundary energy.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266453","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 : 2024-09-18DOI: 10.1103/physrevmaterials.8.094604
Ymir K. Frodason, Augustinas Galeckas, Vegard S. Olsen, Philip M. Weiser, Zbigniew Galazka, Chris G. Van de Walle, Lasse Vines
This work explores the luminescence properties of melt-grown single crystals using photoluminescence spectroscopy and first-principles calculations. The photoluminescence spectra consist of numerous overlapping broad bands in the spectral range between 1.4 and 3.9 eV, which can be divided into low- (1.4–2.7 eV) and high-energy (2.7–3.9 eV) parts. When using below-gap excitation, the photoluminescence spectrum shows distinct orange and ultraviolet luminescence bands peaking at 1.99 and 3.36 eV, respectively. The results are interpreted by using configuration coordinate diagrams derived from hybrid functional calculations for self-trapped holes, as well as for the most stable native defects and their complexes. The calculations show that self-trapped holes, Zn antisites, and Zn-Ga antisite pairs give rise to strongly overlapping luminescence lines that are compatible with the high-energy side of the broad emission. For the low-energy side, we suggest Zn vacancies and their complexes with Ga antisites as potential intrinsic origins. The calculated Zn vacancy lineshape fits well with the orange luminescence band. Ga vacancies are unlikely to be the origin of the observed visible and ultraviolet emission, as the calculated luminescence lines occur in the infrared region. Moreover, complexes between the Ga vacancy and one or two Ga antisites, which would show luminescence at higher energies, are only metastable. It is more favorable for a Ga antisite to jump into the Ga vacancy, replacing the Ga antisite and vacancy with a Zn vacancy.
这项研究利用光致发光光谱和第一原理计算探讨了熔融生长的 ZnGa2O4 单晶的发光特性。光致发光光谱由 1.4 至 3.9 eV 光谱范围内的许多重叠宽带组成，可分为低能（1.4-2.7 eV）和高能（2.7-3.9 eV）两部分。当使用低于隙激发时，光致发光光谱显示出明显的橙色和紫外发光带，峰值分别为 1.99 和 3.36 eV。利用混合函数计算得出的配置坐标图解释了自俘获空穴以及最稳定的原生缺陷及其复合物的结果。计算结果表明，自俘获空穴、Zn 反异质体和 Zn-Ga 反异质体对会产生强烈重叠的发光线，这些发光线与宽发射的高能侧相符。对于低能侧，我们建议将锌空位及其与镓反相石的复合物作为潜在的内在来源。计算得出的 Zn 空位线形与橙色发光带非常吻合。镓空位不太可能是观测到的可见光和紫外线发射的来源，因为计算出的发光线出现在红外区域。此外，镓空位与一个或两个镓对位体之间的络合物会在更高能量下发光，但这种络合物只能是稳定的。一个 Ga 反杂质跃迁到 Ga 空位中，用一个 Zn 空位取代 Ga 反杂质和空位，这对 Ga 空位更有利。
{"title":"Intrinsic origins of broad luminescence in melt-grown ZnGa2O4 single crystals","authors":"Ymir K. Frodason, Augustinas Galeckas, Vegard S. Olsen, Philip M. Weiser, Zbigniew Galazka, Chris G. Van de Walle, Lasse Vines","doi":"10.1103/physrevmaterials.8.094604","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094604","url":null,"abstract":"This work explores the luminescence properties of melt-grown <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>ZnGa</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>4</mn></msub></mrow></math> single crystals using photoluminescence spectroscopy and first-principles calculations. The photoluminescence spectra consist of numerous overlapping broad bands in the spectral range between 1.4 and 3.9 eV, which can be divided into low- (1.4–2.7 eV) and high-energy (2.7–3.9 eV) parts. When using below-gap excitation, the photoluminescence spectrum shows distinct orange and ultraviolet luminescence bands peaking at 1.99 and 3.36 eV, respectively. The results are interpreted by using configuration coordinate diagrams derived from hybrid functional calculations for self-trapped holes, as well as for the most stable native defects and their complexes. The calculations show that self-trapped holes, Zn antisites, and Zn-Ga antisite pairs give rise to strongly overlapping luminescence lines that are compatible with the high-energy side of the broad emission. For the low-energy side, we suggest Zn vacancies and their complexes with Ga antisites as potential intrinsic origins. The calculated Zn vacancy lineshape fits well with the orange luminescence band. Ga vacancies are unlikely to be the origin of the observed visible and ultraviolet emission, as the calculated luminescence lines occur in the infrared region. Moreover, complexes between the Ga vacancy and one or two Ga antisites, which would show luminescence at higher energies, are only metastable. It is more favorable for a Ga antisite to jump into the Ga vacancy, replacing the Ga antisite and vacancy with a Zn vacancy.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266456","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 : 2024-09-18DOI: 10.1103/physrevmaterials.8.094407
J. Sridhar Mohanty, Saheli Samanta, Kalyan Mandal
Coupled first-order magnetostructural transformations (FOMSTs) with narrow widths governed by low external stimuli play a crucial role in magnetic refrigeration for ferromagnetic hexagonal systems. In this work, we report a family of magnetocaloric materials named boron (B)-doped compounds that are devoid of rare-earth elements. Our results show that varying B concentrations up to 5 at. % can tailor the robust FOMSTs between the low-temperature ferromagnetic orthorhombic phase and the high-temperature paramagnetic hexagonal phase in a wider temperature regime. A dramatic change in hysteresis () from ∼25 K for to ∼8 (9) K as well as increases in the saturation magnetization for specific 2 (3) at. % of B dopants is pronounced. Henceforth, the origin of the reducing hysteresis is illustrated based on the geometrical compatibility conditions between the austenite and martensite phases using temperature-dependent powder x-ray diffraction analysis. Moreover, we found the samples performed with good functional stability from the thermal cycling run. The branch of these B doping materials exhibits robust features of a large magnetocaloric effect (MCE) over an extensive temperature range (∼71 K) and temperature-averaged magnetic entropy change at a lower magnetic field change of 2 T. These several tangible benefits, such as reduced , geometrical compatibility, and robust MCE properties are first reported in the studied hexagonal system. Therefore, our results offer a viable approach to improve the cascading of these materials towards the application of cooling technology.
在铁磁性六方体系的磁制冷过程中，由低外部刺激控制的窄宽度耦合一阶磁结构转变（FOMST）起着至关重要的作用。在这项研究中，我们报告了一系列不含稀土元素的磁致冷材料，它们被命名为掺硼（B）的 (MnNiSi)0.67(Fe2Ge)0.33 化合物。我们的研究结果表明，改变硼的浓度（最高可达 5 at.当 x=0 时，磁滞（ΔThys）从 ∼25 K 急剧下降到 ∼8 (9) K，同时饱和磁化率在特定的 2 (3) at.B掺杂剂的百分比明显增加。因此，我们利用随温度变化的粉末 X 射线衍射分析，根据奥氏体和马氏体相之间的几何相容性条件 (λ2∼1) 来说明还原磁滞的起源。此外，我们还发现样品在热循环运行中具有良好的功能稳定性。这些掺 B 材料的分支在很大的温度范围（∼ 71 K）内表现出强大的磁致效应（MCE），并在较低的磁场变化 2 T 时表现出温度平均磁熵变化。因此，我们的研究结果为改进这些材料的级联以应用冷却技术提供了一种可行的方法。
{"title":"Subjugating extensive magnetostructural temperature window and giant magnetocaloric effect in B-doped (MnNiSi)0.67(Fe2Ge)0.33 hexagonal system","authors":"J. Sridhar Mohanty, Saheli Samanta, Kalyan Mandal","doi":"10.1103/physrevmaterials.8.094407","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094407","url":null,"abstract":"Coupled first-order magnetostructural transformations (FOMSTs) with narrow widths governed by low external stimuli play a crucial role in magnetic refrigeration for ferromagnetic hexagonal systems. In this work, we report a family of magnetocaloric materials named boron (B)-doped <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mrow><mo>(</mo><mi>MnNiSi</mi><mo>)</mo></mrow><mrow><mn>0.67</mn></mrow></msub><msub><mrow><mo>(</mo><mrow><mi mathvariant=\"normal\">F</mi><msub><mi mathvariant=\"normal\">e</mi><mn>2</mn></msub><mi>Ge</mi></mrow><mo>)</mo></mrow><mrow><mn>0.33</mn></mrow></msub></mrow></math> compounds that are devoid of rare-earth elements. Our results show that varying B concentrations up to 5 at. % can tailor the robust FOMSTs between the low-temperature ferromagnetic orthorhombic phase and the high-temperature paramagnetic hexagonal phase in a wider temperature regime. A dramatic change in hysteresis (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">Δ</mi><msub><mi>T</mi><mi>hys</mi></msub></mrow></math>) from ∼25 K for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>=</mo><mn>0</mn></mrow></math> to ∼8 (9) K as well as increases in the saturation magnetization for specific 2 (3) at. % of B dopants is pronounced. Henceforth, the origin of the reducing hysteresis is illustrated based on the geometrical compatibility conditions <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><msub><mi>λ</mi><mn>2</mn></msub><mo>∼</mo><mn>1</mn><mo>)</mo></mrow></math> between the austenite and martensite phases using temperature-dependent powder x-ray diffraction analysis. Moreover, we found the samples performed with good functional stability from the thermal cycling run. The branch of these B doping materials exhibits robust features of a large magnetocaloric effect (MCE) over an extensive temperature range (∼71 K) and temperature-averaged magnetic entropy change at a lower magnetic field change of 2 T. These several tangible benefits, such as reduced <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">Δ</mi><msub><mi>T</mi><mi>hys</mi></msub></mrow></math>, geometrical compatibility, and robust MCE properties are first reported in the studied hexagonal system. Therefore, our results offer a viable approach to improve the cascading of these materials towards the application of cooling technology.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266613","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 : 2024-09-17DOI: 10.1103/physrevmaterials.8.093608
X. T. Li, Z. Q. Liu, Z. J. Zhang, P. Zhang, Z. F. Zhang
In principle, the ductile-to-brittle transition (DBT) of metallic glasses may be dominated by the competition between shearing and cracking at different stress states. In response to this issue, we propose a new and concise criterion for DBT, named as the shearing-cracking (S-C) criterion, which can accurately predict the critical transition behaviors in metallic glasses induced by variations in both stress state (extrinsic factor) and Poisson's ratio (intrinsic factor). Furthermore, the S-C criterion provides a reasonable explanation for the peculiar phenomenon in metallic glasses that there are rare experimental cases of tensile fracture angle within the range of to . Importantly, the S-C criterion offers theoretical guidance for toughness enhancement in metallic glasses from both intrinsic and extrinsic factors, thus facilitating the advancement of engineering applications involving metallic glasses.
{"title":"Ductile-to-brittle transition criterion of metallic glasses","authors":"X. T. Li, Z. Q. Liu, Z. J. Zhang, P. Zhang, Z. F. Zhang","doi":"10.1103/physrevmaterials.8.093608","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093608","url":null,"abstract":"In principle, the ductile-to-brittle transition (DBT) of metallic glasses may be dominated by the competition between shearing and cracking at different stress states. In response to this issue, we propose a new and concise criterion for DBT, named as the shearing-cracking (S-C) criterion, which can accurately predict the critical transition behaviors in metallic glasses induced by variations in both stress state (extrinsic factor) and Poisson's ratio (intrinsic factor). Furthermore, the S-C criterion provides a reasonable explanation for the peculiar phenomenon in metallic glasses that there are rare experimental cases of tensile fracture angle within the range of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>60</mn><mo>∘</mo></msup></math> to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>90</mn><mo>∘</mo></msup></math>. Importantly, the S-C criterion offers theoretical guidance for toughness enhancement in metallic glasses from both intrinsic and extrinsic factors, thus facilitating the advancement of engineering applications involving metallic glasses.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266610","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 : 2024-09-16DOI: 10.1103/physrevmaterials.8.093607
Amith Adoor Cheenady, Krishna Rajan
Lead-based metal halide perovskites (MHPs) have wide-ranging applications as solar cells, field-effect transistors, diodes, and photodetectors. However, their poor stability and concerns about toxicity have enabled lead-free tin-based MHPs to emerge as a promising alternative. We utilize molecular dynamics (MD) simulations to investigate the anisotropic mechanical behavior of single-crystal cubic , a promising lead-free MHP, under uniaxial tension. Among the three investigated crystal orientations, [111] is found to be the strongest and to exhibit the highest ultimate strain while [100] is the weakest. While shear strain localization and amorphization precede fracture along [100], fracture directly follows strain localization along [110] and [111]. We also investigated the influence of a crystal defect, in the form of an embedded rectangular crack, on the anisotropic mechanical behavior of cubic . The presence of crystal defects is found to substantially reduce the anisotropy in mechanical properties, with very similar crack growth behavior and almost identical stress-strain response noted along starkly different crystal orientations of loading. Finally, the ultimate strengths and ultimate strains of cubic determined here are comparable to or higher than those of cubic and determined in prior MD-based investigations. Thus, our study supports the applicability of cubic as a lead-free alternative to commonly used cubic MHPs, while the sensitivity to crystal defects revealed here underlines the importance of defect control for obtaining robust devices with reliable properties.
{"title":"Anisotropic mechanical behavior of cesium tin iodide perovskite subjected to uniaxial tension","authors":"Amith Adoor Cheenady, Krishna Rajan","doi":"10.1103/physrevmaterials.8.093607","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093607","url":null,"abstract":"Lead-based metal halide perovskites (MHPs) have wide-ranging applications as solar cells, field-effect transistors, diodes, and photodetectors. However, their poor stability and concerns about toxicity have enabled lead-free tin-based MHPs to emerge as a promising alternative. We utilize molecular dynamics (MD) simulations to investigate the anisotropic mechanical behavior of single-crystal cubic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>CsSn</mi><msub><mi mathvariant=\"normal\">I</mi><mn>3</mn></msub></mrow></math>, a promising lead-free MHP, under uniaxial tension. Among the three investigated crystal orientations, [111] is found to be the strongest and to exhibit the highest ultimate strain while [100] is the weakest. While shear strain localization and amorphization precede fracture along [100], fracture directly follows strain localization along [110] and [111]. We also investigated the influence of a crystal defect, in the form of an embedded rectangular crack, on the anisotropic mechanical behavior of cubic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>CsSn</mi><msub><mi mathvariant=\"normal\">I</mi><mn>3</mn></msub></mrow></math>. The presence of crystal defects is found to substantially reduce the anisotropy in mechanical properties, with very similar crack growth behavior and almost identical stress-strain response noted along starkly different crystal orientations of loading. Finally, the ultimate strengths and ultimate strains of cubic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>CsSn</mi><msub><mi mathvariant=\"normal\">I</mi><mn>3</mn></msub></mrow></math> determined here are comparable to or higher than those of cubic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>CsPb</mi><msub><mi mathvariant=\"normal\">I</mi><mn>3</mn></msub></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>MAPb</mi><msub><mi mathvariant=\"normal\">I</mi><mn>3</mn></msub></mrow></math> determined in prior MD-based investigations. Thus, our study supports the applicability of cubic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>CsSn</mi><msub><mi mathvariant=\"normal\">I</mi><mn>3</mn></msub></mrow></math> as a lead-free alternative to commonly used cubic MHPs, while the sensitivity to crystal defects revealed here underlines the importance of defect control for obtaining robust devices with reliable properties.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266611","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 : 2024-09-16DOI: 10.1103/physrevmaterials.8.096001
Brendan McBennett, Yuka Esashi, Nicholas W. Jenkins, Albert Beardo, Yunzhe Shao, Emma E. Nelson, Theodore H. Culman, Begoña Abad, Michael Tanksalvala, Travis D. Frazer, Samuel Marks, Weilun Chao, Sadegh Yazdi, Joshua L. Knobloch, Henry C. Kapteyn, Margaret M. Murnane
Next-generation nanoelectronic, energy, and quantum technologies require increasingly stringent thermal, optical, mechanical, and electrical properties of component materials, often surpassing the limits of widely used materials such as silicon. Diamond, an ultrawide bandgap semiconductor, is a promising material for these applications because of its very high stiffness, thermal conductivity, and electron mobility. However, incorporating diamond into devices that require high-quality metal-diamond interfaces is challenging. In this work, we use a suite of electron microscopy measurements to reveal an ultrathin amorphous carbon layer that emerges at metal-diamond interfaces after electron beam lithography. Using extreme ultraviolet scatterometry, we nondestructively determine lower bounds on the layer's Young's modulus and thermal conductivity, which at and W/() are indicative of a diamondlike form of amorphous carbon with high bonding. However, extreme ultraviolet coherent diffractive imaging reflectometry and energy-dispersive x-ray spectroscopy measurements indicate a low and likely inhomogeneous density in the range of . The low density of such a stiff and conductive layer could indicate that it contains nanometer-scale voids or atomic-scale vacancies. The appearance of this unusual layer illustrates the nanofabrication challenges for diamond and highlights the need for better techniques to characterize surfaces and interfaces in nanoscale devices.
{"title":"Low-density diamondlike amorphous carbon at nanostructured metal-diamond interfaces","authors":"Brendan McBennett, Yuka Esashi, Nicholas W. Jenkins, Albert Beardo, Yunzhe Shao, Emma E. Nelson, Theodore H. Culman, Begoña Abad, Michael Tanksalvala, Travis D. Frazer, Samuel Marks, Weilun Chao, Sadegh Yazdi, Joshua L. Knobloch, Henry C. Kapteyn, Margaret M. Murnane","doi":"10.1103/physrevmaterials.8.096001","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.096001","url":null,"abstract":"Next-generation nanoelectronic, energy, and quantum technologies require increasingly stringent thermal, optical, mechanical, and electrical properties of component materials, often surpassing the limits of widely used materials such as silicon. Diamond, an ultrawide bandgap semiconductor, is a promising material for these applications because of its very high stiffness, thermal conductivity, and electron mobility. However, incorporating diamond into devices that require high-quality metal-diamond interfaces is challenging. In this work, we use a suite of electron microscopy measurements to reveal an ultrathin amorphous carbon layer that emerges at metal-diamond interfaces after electron beam lithography. Using extreme ultraviolet scatterometry, we nondestructively determine lower bounds on the layer's Young's modulus and thermal conductivity, which at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>></mo><mn>230</mn><mspace width=\"4pt\"></mspace><mi>GPa</mi></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>></mo><mn>1.1</mn></mrow></math> W/(<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"normal\">m</mi><mspace width=\"0.16em\"></mspace><mi mathvariant=\"normal\">K</mi></mrow></math>) are indicative of a diamondlike form of amorphous carbon with high <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mi>s</mi><mi>p</mi></mrow><mn>3</mn></msup></math> bonding. However, extreme ultraviolet coherent diffractive imaging reflectometry and energy-dispersive x-ray spectroscopy measurements indicate a low and likely inhomogeneous density in the range of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>–</mo><mn>2</mn><mspace width=\"4pt\"></mspace><msup><mrow><mi mathvariant=\"normal\">g</mi><mo>/</mo><mi>cm</mi></mrow><mn>3</mn></msup></mrow></math>. The low density of such a stiff and conductive layer could indicate that it contains nanometer-scale voids or atomic-scale vacancies. The appearance of this unusual layer illustrates the nanofabrication challenges for diamond and highlights the need for better techniques to characterize surfaces and interfaces in nanoscale devices.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266615","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 : 2024-09-16DOI: 10.1103/physrevmaterials.8.094603
Chaiyawat Kaewmeechai, Jack Strand, Alexander Shluger
We investigate the structural, electronic, and optical properties of oxygen vacancies () in crystalline , and using density functional theory (DFT) calculations with the PBE0-TC-LRC functional. Our results reveal that the charge transition levels (CTLs) associated with exhibit significant variations depending on the crystal phase and the coordination environment of surrounding atoms. In particular, surrounded by tetrahedral Ga atoms () exhibit deeper CTLs compared to those surrounded by octahedral Ga atoms (). We also observe distinct atomic relaxations, with larger displacements of atoms compared to atoms in the vicinity of . Using linear-response time-dependent DFT, we investigate the optical transitions of and identify two distinct types of transitions: defect state to conduction band state and valence band to defect state. These results can be used to better understand the optical properties of defects in films.
我们使用 PBE0-TC-LRC 函数进行密度泛函理论（DFT）计算，研究了晶体 α、β 和 ε-Ga2O3 中氧空位（VO）的结构、电子和光学性质。我们的研究结果表明，与 VO 相关的电荷转移水平（CTLs）会因晶体相和周围原子的配位环境而发生显著变化。特别是，与被八面体镓原子（O-Ga）包围的 VO 相比，被四面体镓原子（T-Ga）包围的 VO 显示出更深的 CTL。我们还观察到不同的原子弛豫，与 VO 附近的 O-Ga 原子相比，T-Ga 原子的位移更大。利用线性响应时间相关 DFT，我们研究了 VO 的光学跃迁，并确定了两种不同类型的跃迁：缺陷态到传导带态和价带到缺陷态。这些结果可用于更好地理解 Ga2O3 薄膜中 VO 缺陷的光学特性。
{"title":"Role of local structure in the optical and electronic properties of oxygen vacancies in different crystal phases of Ga2O3","authors":"Chaiyawat Kaewmeechai, Jack Strand, Alexander Shluger","doi":"10.1103/physrevmaterials.8.094603","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.094603","url":null,"abstract":"We investigate the structural, electronic, and optical properties of oxygen vacancies (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">V</mi><mi mathvariant=\"normal\">O</mi></msub></math>) in crystalline <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>α</mi><mo>,</mo><mo> </mo><mi>β</mi></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>ε</mi><mtext>−</mtext><msub><mi>Ga</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>3</mn></msub></mrow></math> using density functional theory (DFT) calculations with the PBE0-TC-LRC functional. Our results reveal that the charge transition levels (CTLs) associated with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">V</mi><mi mathvariant=\"normal\">O</mi></msub></math> exhibit significant variations depending on the crystal phase and the coordination environment of surrounding atoms. In particular, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mi mathvariant=\"normal\">O</mi></msub><mi mathvariant=\"normal\">s</mi></mrow></math> surrounded by tetrahedral Ga atoms (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>T</mi><mtext>-Ga</mtext></mrow></math>) exhibit deeper CTLs compared to those surrounded by octahedral Ga atoms (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>O</mi><mtext>-Ga</mtext></mrow></math>). We also observe distinct atomic relaxations, with larger displacements of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>T</mi><mtext>-Ga</mtext></mrow></math> atoms compared to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>O</mi><mtext>-Ga</mtext></mrow></math> atoms in the vicinity of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mi mathvariant=\"normal\">O</mi></msub><mi mathvariant=\"normal\">s</mi></mrow></math>. Using linear-response time-dependent DFT, we investigate the optical transitions of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">V</mi><mi mathvariant=\"normal\">O</mi></msub></math> and identify two distinct types of transitions: defect state to conduction band state and valence band to defect state. These results can be used to better understand the optical properties of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">V</mi><mi mathvariant=\"normal\">O</mi></msub></math> defects in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Ga</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>3</mn></msub></mrow></math> films.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266612","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 : 2024-09-16DOI: 10.1103/physrevmaterials.8.093606
Ian Chesser, Peter M. Derlet, Avanish Mishra, Sarah Paguaga, Nithin Mathew, Khanh Dang, Blas Pedro Uberuaga, Abigail Hunter, Saryu Fensin
The microstructural evolution at and near preexisting grain boundaries (GBs) and dislocations in materials under high radiation doses is still poorly understood. In this work, we use the creation relaxation algorithm (CRA) developed for atomistic modeling of high-dose irradiation in bulk materials to probe the athermal limit of saturation of GB and dislocation core regions under irradiation in fcc Ni. We find that, upon continuously subjecting a single dislocation or GB to Frenkel pair creation in the athermal limit, a local steady-state disordered defect structure is reached with excess properties that fluctuate around constant values. Case studies are given for a straight screw dislocation which elongates into a helix under irradiation and several types of low- and high-angle GBs, which exhibit coupled responses such as absorption of extrinsic dislocations, roughening, and migration. A positive correlation is found between the initial GB energy and the local steady-state GB energy under irradiation across a wide variety of GB types. Metastable GB structures with similar density in the defect core region but different initial configurations are found to converge to the same limiting structure under CRA. The mechanical responses of pristine and irradiated dislocations and GB structures are compared under an applied shear stress. Irradiated screw and edge dislocations are found to exhibit a hardening response, migrating at larger flow stresses than their pristine counterparts. Mobile GBs are found to exhibit softening or hardening responses depending on GB character. Although some GBs recover their initial pristine structures upon migration outside of the radiation zone, many GBs sustain different flow stresses corresponding to altered mobile core structures.
{"title":"Structure and migration of heavily irradiated grain boundaries and dislocations in Ni in the athermal limit","authors":"Ian Chesser, Peter M. Derlet, Avanish Mishra, Sarah Paguaga, Nithin Mathew, Khanh Dang, Blas Pedro Uberuaga, Abigail Hunter, Saryu Fensin","doi":"10.1103/physrevmaterials.8.093606","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.093606","url":null,"abstract":"The microstructural evolution at and near preexisting grain boundaries (GBs) and dislocations in materials under high radiation doses is still poorly understood. In this work, we use the creation relaxation algorithm (CRA) developed for atomistic modeling of high-dose irradiation in bulk materials to probe the athermal limit of saturation of GB and dislocation core regions under irradiation in fcc Ni. We find that, upon continuously subjecting a single dislocation or GB to Frenkel pair creation in the athermal limit, a local steady-state disordered defect structure is reached with excess properties that fluctuate around constant values. Case studies are given for a straight screw dislocation which elongates into a helix under irradiation and several types of low- and high-angle GBs, which exhibit coupled responses such as absorption of extrinsic dislocations, roughening, and migration. A positive correlation is found between the initial GB energy and the local steady-state GB energy under irradiation across a wide variety of GB types. Metastable GB structures with similar density in the defect core region but different initial configurations are found to converge to the same limiting structure under CRA. The mechanical responses of pristine and irradiated dislocations and GB structures are compared under an applied shear stress. Irradiated screw and edge dislocations are found to exhibit a hardening response, migrating at larger flow stresses than their pristine counterparts. Mobile GBs are found to exhibit softening or hardening responses depending on GB character. Although some GBs recover their initial pristine structures upon migration outside of the radiation zone, many GBs sustain different flow stresses corresponding to altered mobile core structures.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142266614","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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