Soumya Biswas, Keshav Dabral, Saptak Majumder, Rajasekar Parasuraman, Aditya S. Dutt, Vinayak B. Kamble
Among the popular TE materials, selenides and tellurides are the benchmarks of high-efficiency systems. However, for the high-temperature application (>700 K), it is required to rely on the silicides and the oxides due to their exceptional thermal stability. ZnO is among the first few oxides in the field of thermoelectricity. Al-doped ZnO is a proven material for its high-temperature thermoelectric applications. However, the high grain boundary resistance limits further improvement of the efficiency of this oxide. Band-engineering, band-modification is a successful approach in lowering the grain boundary resistance. The addition of graphite and graphite-based materials at the grain boundaries is shown to serve this purpose. In this work, graphite powder is added in varying proportions to Al-doped ZnO triangular microcrystals. Thus, prepared materials are characterized to confirm the formation and investigate the nature of interface, morphology, etc. TE parameters such as electrical conductivity, Seebeck coefficient, and thermal conductivity of those materials also have been measured. The theoretical calculation of TE efficiency zT often differs from the actual experimental results due to the wide range of preparation methods, leading to changes in porosity, the nature and density defects, and several other factors. In this paper, an effort has been made to estimate the maximum achievable power factor (PFmax) from the measured TE parameters of this set of samples by the Jonker and Ioffe analysis. Based on the predicted PFmax, an appropriate material composition has been identified to achieve that same. Subsequently, including the measured parameters the TE efficiency (zT) is calculated. Further, a sudden dip observed in the thermal conductivity at the high-temperature range (625 K - 1000 K) of the prepared undoped ZnO graphite composite is investigated in this paper.
在常用的 TE 材料中，硒化物和碲化物是高效系统的基准。然而，对于高温应用（>700K），由于硅化物和氧化物具有卓越的热稳定性，因此需要依靠它们。氧化锌是热电领域最早出现的几种氧化物之一。掺铝氧化锌是一种成熟的高温热电应用材料。然而，高晶界电阻限制了这种氧化物效率的进一步提高。在晶界添加石墨和石墨基材料就能达到这一目的。在这项研究中，不同比例的石墨粉被添加到铝掺杂的氧化锌三角微晶中。因此，对制备的材料进行了表征，以确认其形貌并研究界面、形态等的性质。此外，还测量了这些材料的电导率、塞贝克系数和热导率等 TE 参数。由于制备方法多种多样，导致孔隙率、缺陷性质和密度以及其他一些因素发生变化，因此 TE 效率 zT 的理论计算结果往往与实际实验结果不同。本文试图通过 Jonker 和 Ioffe 分析法，从这组样品的测量 TE 参数中估算出可达到的最大功率因数（PFmax）。根据预测的最大功率因数，确定了实现该值的适当材料组成。随后，通过测量参数计算出 TE 效率 (zT)。此外，本文还对制备的未掺杂氧化锌石墨复合材料在高温范围（625 K -1000 K）内的热导率突然下降进行了研究。
{"title":"Predicting of the Realizable Maximum Power Factor using the Jonker and Ioffe formulation: Al-doped ZnO Triangular Microcrystals with Graphite Inclusion Case Study","authors":"Soumya Biswas, Keshav Dabral, Saptak Majumder, Rajasekar Parasuraman, Aditya S. Dutt, Vinayak B. Kamble","doi":"arxiv-2409.09728","DOIUrl":"https://doi.org/arxiv-2409.09728","url":null,"abstract":"Among the popular TE materials, selenides and tellurides are the benchmarks\u0000of high-efficiency systems. However, for the high-temperature application (>700\u0000K), it is required to rely on the silicides and the oxides due to their\u0000exceptional thermal stability. ZnO is among the first few oxides in the field\u0000of thermoelectricity. Al-doped ZnO is a proven material for its\u0000high-temperature thermoelectric applications. However, the high grain boundary\u0000resistance limits further improvement of the efficiency of this oxide.\u0000Band-engineering, band-modification is a successful approach in lowering the\u0000grain boundary resistance. The addition of graphite and graphite-based\u0000materials at the grain boundaries is shown to serve this purpose. In this work,\u0000graphite powder is added in varying proportions to Al-doped ZnO triangular\u0000microcrystals. Thus, prepared materials are characterized to confirm the\u0000formation and investigate the nature of interface, morphology, etc. TE\u0000parameters such as electrical conductivity, Seebeck coefficient, and thermal\u0000conductivity of those materials also have been measured. The theoretical\u0000calculation of TE efficiency zT often differs from the actual experimental\u0000results due to the wide range of preparation methods, leading to changes in\u0000porosity, the nature and density defects, and several other factors. In this\u0000paper, an effort has been made to estimate the maximum achievable power factor\u0000(PFmax) from the measured TE parameters of this set of samples by the Jonker\u0000and Ioffe analysis. Based on the predicted PFmax, an appropriate material\u0000composition has been identified to achieve that same. Subsequently, including\u0000the measured parameters the TE efficiency (zT) is calculated. Further, a sudden\u0000dip observed in the thermal conductivity at the high-temperature range (625 K -\u00001000 K) of the prepared undoped ZnO graphite composite is investigated in this\u0000paper.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xingyue Shi, Linming Zhou, Yuhui Huang, Yongjun Wu, Zijian Hong
In the dynamic and rapidly advancing battery field, alloy anode materials are a focal point due to their superior electrochemical performance. Traditional screening methods are inefficient and time-consuming. Our research introduces a machine learning-assisted strategy to expedite the discovery and optimization of these materials. We compiled a vast dataset from the MP and AFLOW databases, encompassing tens of thousands of alloy compositions and properties. Utilizing a CGCNN, we accurately predicted the potential and specific capacity of alloy anodes, validated against experimental data. This approach identified approximately 120 low potential and high specific capacity alloy anodes suitable for various battery systems including Li, Na, K, Zn, Mg, Ca, and Al-based. Our method not only streamlines the screening of battery anode materials but also propels the advancement of battery material research and innovation in energy storage technology.
{"title":"Machine learning assisted screening of metal binary alloys for anode materials","authors":"Xingyue Shi, Linming Zhou, Yuhui Huang, Yongjun Wu, Zijian Hong","doi":"arxiv-2409.09583","DOIUrl":"https://doi.org/arxiv-2409.09583","url":null,"abstract":"In the dynamic and rapidly advancing battery field, alloy anode materials are\u0000a focal point due to their superior electrochemical performance. Traditional\u0000screening methods are inefficient and time-consuming. Our research introduces a\u0000machine learning-assisted strategy to expedite the discovery and optimization\u0000of these materials. We compiled a vast dataset from the MP and AFLOW databases,\u0000encompassing tens of thousands of alloy compositions and properties. Utilizing\u0000a CGCNN, we accurately predicted the potential and specific capacity of alloy\u0000anodes, validated against experimental data. This approach identified\u0000approximately 120 low potential and high specific capacity alloy anodes\u0000suitable for various battery systems including Li, Na, K, Zn, Mg, Ca, and\u0000Al-based. Our method not only streamlines the screening of battery anode\u0000materials but also propels the advancement of battery material research and\u0000innovation in energy storage technology.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding lattice dynamics and thermal transport in crystalline compounds with intrinsically low lattice thermal conductivity ($kappa_L$) is crucial in condensed matter physics. In this work, we investigate the lattice thermal conductivity of crystalline CsCu$_4$Se$_3$ by coupling first-principles anharmonic lattice dynamics with a unified theory of thermal transport. We consider the effects of both cubic and quartic anharmonicity on phonon scattering and energy shifts, as well as the diagonal and off-diagonal terms of heat flux operators. Our results reveal that the vibrational properties of CsCu$_4$Se$_3$ are characterized by strong anharmonicity and wave-like phonon tunneling. In particular, the strong three- and four-phonon scattering induced by Cu atoms significantly suppresses particle-like propagation while enhancing wave-like tunneling. Moreover, the coherence-driven conductivity dominates the total thermal conductivity along the $z$-axis, leading to an anomalous, wide-temperature-range (100-700 K) glassy-like thermal transport. Importantly, the significant coherence contribution, resulting from the coupling of distinct vibrational eigenstates, facilitates efficient thermal transport across layers, sharply contrasting with traditional layered materials. Finally, we established a criterion linking anharmonic scattering to the frequency differences between eigenstates, which effectively explains the non-monotonic temperature dependence of coherence thermal conductivity. Our work not only reveals the impact of higher-order anharmonic self-energies in crystalline CsCu$_4$Se$_3$, but also examines the dynamic evolution of wave-like thermal conductivity, providing insights into the microscopic mechanisms driving anomalous heat transport.
{"title":"High-order Anharmonic Scattering and Wide-Temperature-Range Glassy Thermal Transport in Crystalline CsCu$_4$Se$_3$","authors":"Jincheng Yue, Yanhui Liu, Jiongzhi Zheng","doi":"arxiv-2409.09594","DOIUrl":"https://doi.org/arxiv-2409.09594","url":null,"abstract":"Understanding lattice dynamics and thermal transport in crystalline compounds\u0000with intrinsically low lattice thermal conductivity ($kappa_L$) is crucial in\u0000condensed matter physics. In this work, we investigate the lattice thermal\u0000conductivity of crystalline CsCu$_4$Se$_3$ by coupling first-principles\u0000anharmonic lattice dynamics with a unified theory of thermal transport. We\u0000consider the effects of both cubic and quartic anharmonicity on phonon\u0000scattering and energy shifts, as well as the diagonal and off-diagonal terms of\u0000heat flux operators. Our results reveal that the vibrational properties of\u0000CsCu$_4$Se$_3$ are characterized by strong anharmonicity and wave-like phonon\u0000tunneling. In particular, the strong three- and four-phonon scattering induced\u0000by Cu atoms significantly suppresses particle-like propagation while enhancing\u0000wave-like tunneling. Moreover, the coherence-driven conductivity dominates the\u0000total thermal conductivity along the $z$-axis, leading to an anomalous,\u0000wide-temperature-range (100-700 K) glassy-like thermal transport. Importantly,\u0000the significant coherence contribution, resulting from the coupling of distinct\u0000vibrational eigenstates, facilitates efficient thermal transport across layers,\u0000sharply contrasting with traditional layered materials. Finally, we established\u0000a criterion linking anharmonic scattering to the frequency differences between\u0000eigenstates, which effectively explains the non-monotonic temperature\u0000dependence of coherence thermal conductivity. Our work not only reveals the\u0000impact of higher-order anharmonic self-energies in crystalline CsCu$_4$Se$_3$,\u0000but also examines the dynamic evolution of wave-like thermal conductivity,\u0000providing insights into the microscopic mechanisms driving anomalous heat\u0000transport.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study introduces a novel approach for crystal structure analysis, utilizing Inverse EXAFS Analysis (IEA). To assess the reliability of IEA, we applied it to various experimentally studied materials, including LiCrO2 and CuFeO2. Our findings demonstrate that IEA offers a promising alternative to traditional techniques like XRD, particularly in cases where instrumentation or crystal structure defects pose challenges. IEA effectively revealed the crystal structures of both LiCrO2 and CuFeO2, demonstrating its ability to accurately characterize complex materials. The technique's potential to enhance XAFS data analysis is significant, providing researchers with a valuable tool for crystal structure determination. Future developments in IEA could further expand its capabilities and make it a more accessible and efficient method for materials scientists.
{"title":"Crystal Structure Determination via Inverse EXAFS Analysis: A Comparative Study Utilizing the Demeter Software Package","authors":"Osman Murat Ozkendir","doi":"arxiv-2409.09693","DOIUrl":"https://doi.org/arxiv-2409.09693","url":null,"abstract":"This study introduces a novel approach for crystal structure analysis,\u0000utilizing Inverse EXAFS Analysis (IEA). To assess the reliability of IEA, we\u0000applied it to various experimentally studied materials, including LiCrO2 and\u0000CuFeO2. Our findings demonstrate that IEA offers a promising alternative to\u0000traditional techniques like XRD, particularly in cases where instrumentation or\u0000crystal structure defects pose challenges. IEA effectively revealed the crystal\u0000structures of both LiCrO2 and CuFeO2, demonstrating its ability to accurately\u0000characterize complex materials. The technique's potential to enhance XAFS data\u0000analysis is significant, providing researchers with a valuable tool for crystal\u0000structure determination. Future developments in IEA could further expand its\u0000capabilities and make it a more accessible and efficient method for materials\u0000scientists.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sonia Kaushik, Rakhul Raj, Pooja Gupta, R Venkatesh, Andrei Chumakov, Matthias Schwartzkopf, V Raghavendra Reddy, Dileep Kumar
Organic spintronics has drawn the interest of the science community due to various applications in spin-valve devices. However, an efficient room-temperature Organic Spin Valve device has not been experimentally realized due to the complicated spin transport at the metal-organic interfaces. The present study focuses on a comprehensive understanding of the interfacial properties essential for advancing device performance and functionality. The structural and magnetic properties of the ultra-thin Cobalt (Co) films deposited on the fullerene (C60) layer are studied to investigate the origin of magnetic anisotropy in the metal-organic bilayer structures. Due to the mechanical softness of C60, penetration of ferromagnetic Co atoms inside the C60 film is confirmed by the X-ray reflectivity and Secondary Ion Mass Spectroscopy measurements. Grazing incidence small-angle X-ray scattering and atomic force microscopy provided information regarding the structural and morphological properties of the Co/C60 bilayers, angular dependent Magneto-optic Kerr effect measurements with varying Co layer thickness provided information about the growth-induced uniaxial magnetic anisotropy. In contrast to the inorganic silicon substrates, magnetic anisotropy in Co film tends to develop at 25 {AA} thickness on the C60 layer, which further increases with the thickness of Cobalt. The anomalous behavior in coercivity and remanence variation along the nominal hard axis is explained by a two-grain Stoner-Wohlfarth model with intergranular exchange coupling. It is further confirmed by a non-uniform spatial distribution of magnetic domains investigated through Kerr microscopy. These anomalies could be attributed to the distribution of magneto-crystalline anisotropy and inhomogeneous strain caused by the formation of a diffused layer at the Co/C60 interface.
有机自旋电子学在自旋阀器件中的各种应用引起了科学界的兴趣。然而，由于金属-有机界面上复杂的自旋传输，高效的室温有机自旋阀器件尚未在实验中实现。本研究的重点是全面了解对提高器件性能和功能至关重要的界面特性。研究了沉积在富勒烯（C60）层上的超薄钴（Co）薄膜的结构和磁特性，以探讨金属有机双层结构中磁各向异性的起源。由于 C60 的机械软性，铁磁性 Co 原子在 C60 薄膜内部的渗透通过 X 射线反射率和二次离子质谱测量得到了证实。掠入射小角 X 射线散射和原子力显微镜提供了有关 Co/C60 双层膜的结构和形态特性的信息，不同 Co 层厚度的角度依赖性磁光 Kerr 效应测量提供了有关生长诱导的单轴磁各向异性的信息。与无机硅衬底相比，钴膜中的磁各向异性在 C60 层厚度为 25 {AA} 时趋于发展，并随着钴层厚度的增加而进一步增强。沿标称硬轴的矫顽力和剩磁变化的异常行为可以用晶粒间交换耦合的双晶粒斯顿-沃尔夫模型来解释。通过克尔显微镜研究发现的磁畴非均匀空间分布进一步证实了这一点。这些异常现象可归因于磁晶各向异性的分布和 Co/C60 界面扩散层的形成所导致的不均匀应变。
{"title":"Growth-Induced Unconventional Magnetic Anisotropy in Co/Fullerene (C60) Bilayer Systems; Insights from a Two-Grain Stoner-Wohlfarth Model","authors":"Sonia Kaushik, Rakhul Raj, Pooja Gupta, R Venkatesh, Andrei Chumakov, Matthias Schwartzkopf, V Raghavendra Reddy, Dileep Kumar","doi":"arxiv-2409.10569","DOIUrl":"https://doi.org/arxiv-2409.10569","url":null,"abstract":"Organic spintronics has drawn the interest of the science community due to\u0000various applications in spin-valve devices. However, an efficient\u0000room-temperature Organic Spin Valve device has not been experimentally realized\u0000due to the complicated spin transport at the metal-organic interfaces. The\u0000present study focuses on a comprehensive understanding of the interfacial\u0000properties essential for advancing device performance and functionality. The\u0000structural and magnetic properties of the ultra-thin Cobalt (Co) films\u0000deposited on the fullerene (C60) layer are studied to investigate the origin of\u0000magnetic anisotropy in the metal-organic bilayer structures. Due to the\u0000mechanical softness of C60, penetration of ferromagnetic Co atoms inside the\u0000C60 film is confirmed by the X-ray reflectivity and Secondary Ion Mass\u0000Spectroscopy measurements. Grazing incidence small-angle X-ray scattering and\u0000atomic force microscopy provided information regarding the structural and\u0000morphological properties of the Co/C60 bilayers, angular dependent\u0000Magneto-optic Kerr effect measurements with varying Co layer thickness provided\u0000information about the growth-induced uniaxial magnetic anisotropy. In contrast\u0000to the inorganic silicon substrates, magnetic anisotropy in Co film tends to\u0000develop at 25 {AA} thickness on the C60 layer, which further increases with\u0000the thickness of Cobalt. The anomalous behavior in coercivity and remanence\u0000variation along the nominal hard axis is explained by a two-grain\u0000Stoner-Wohlfarth model with intergranular exchange coupling. It is further\u0000confirmed by a non-uniform spatial distribution of magnetic domains\u0000investigated through Kerr microscopy. These anomalies could be attributed to\u0000the distribution of magneto-crystalline anisotropy and inhomogeneous strain\u0000caused by the formation of a diffused layer at the Co/C60 interface.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dylan A. Folker, Zekun Chen, Giuseppe Barbalinardo, Florian Knoop, Davide Donadio
We describe a theoretical and computational approach to calculate the vibrational, elastic, and thermal properties of materials from the low-temperature quantum regime to the high-temperature anharmonic regime. This approach is based on anharmonic lattice dynamics and the Boltzmann transport equation. It relies on second and third-order force constant tensors estimated by fitting temperature-dependent empirical potentials (TDEP) from path-integral quantum simulations with a first-principles machine learning Hamiltonian. The temperature-renormalized harmonic force constants are used to calculate the elastic moduli and the phonon modes of materials. Harmonic and anharmonic force constants are combined to solve the phonon Boltzmann transport equation to compute the lattice thermal conductivity. We demonstrate the effectiveness of this approach on bulk crystalline silicon in the temperature range from 50 to 1200~K, showing substantial improvement in the prediction of the temperature dependence of the target properties compared to experiments.
{"title":"Elastic moduli and thermal conductivity of quantum materials at finite temperature","authors":"Dylan A. Folker, Zekun Chen, Giuseppe Barbalinardo, Florian Knoop, Davide Donadio","doi":"arxiv-2409.09551","DOIUrl":"https://doi.org/arxiv-2409.09551","url":null,"abstract":"We describe a theoretical and computational approach to calculate the\u0000vibrational, elastic, and thermal properties of materials from the\u0000low-temperature quantum regime to the high-temperature anharmonic regime. This\u0000approach is based on anharmonic lattice dynamics and the Boltzmann transport\u0000equation. It relies on second and third-order force constant tensors estimated\u0000by fitting temperature-dependent empirical potentials (TDEP) from path-integral\u0000quantum simulations with a first-principles machine learning Hamiltonian. The\u0000temperature-renormalized harmonic force constants are used to calculate the\u0000elastic moduli and the phonon modes of materials. Harmonic and anharmonic force\u0000constants are combined to solve the phonon Boltzmann transport equation to\u0000compute the lattice thermal conductivity. We demonstrate the effectiveness of\u0000this approach on bulk crystalline silicon in the temperature range from 50 to\u00001200~K, showing substantial improvement in the prediction of the temperature\u0000dependence of the target properties compared to experiments.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alex Kutana, Koji Shimizu, Satoshi Watanabe, Ryoji Asahi
Graph convolutional neural networks have been instrumental in machine learning of material properties. When representing tensorial properties, weights and descriptors of a physics-informed network must obey certain transformation rules to ensure the independence of the property on the choice of the reference frame. Here we explicitly encode such properties using an equivariant graph convolutional neural network. The network respects rotational symmetries of the crystal throughout by using equivariant weights and descriptors and provides a tensorial output of the target value. Applications to tensors of atomic Born effective charges in diverse materials including perovskite oxides, Li3PO4, and ZrO2, are demonstrated, and good performance and generalization ability is obtained.
{"title":"Representing Born effective charges with equivariant graph convolutional neural networks","authors":"Alex Kutana, Koji Shimizu, Satoshi Watanabe, Ryoji Asahi","doi":"arxiv-2409.08940","DOIUrl":"https://doi.org/arxiv-2409.08940","url":null,"abstract":"Graph convolutional neural networks have been instrumental in machine\u0000learning of material properties. When representing tensorial properties,\u0000weights and descriptors of a physics-informed network must obey certain\u0000transformation rules to ensure the independence of the property on the choice\u0000of the reference frame. Here we explicitly encode such properties using an\u0000equivariant graph convolutional neural network. The network respects rotational\u0000symmetries of the crystal throughout by using equivariant weights and\u0000descriptors and provides a tensorial output of the target value. Applications\u0000to tensors of atomic Born effective charges in diverse materials including\u0000perovskite oxides, Li3PO4, and ZrO2, are demonstrated, and good performance and\u0000generalization ability is obtained.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Layered semiconductors have recently emerged as capable host materials for novel quantum applications ranging from phonics to sensing. Most studies have focused on artificial layered materials, such as hexagonal boron nitride and transitional dichalcogenides. Natural layered materials, such as talc and other silicates, have remained largely unexplored despite their desirable properties, e.g, wide direct bandgap, low concentration of optically active defects, and low abundance of nuclear spins. In this article, we carry out an extensive computational study on pristine and defected talcum layers and discuss their potential applications. After establishing the properties of bulk talc, we study the electronic structure, charge states, spin and optical properties of vacancy defects, metal, metalloid, and non-metallic impurities. We identify several color centers, electron paramagnetic resonance (EPR) centers, potential spin quantum bits, and dopants. These findings advance our understanding of defected talcum layers and point toward potential applications in quantum technologies.
{"title":"Native defects and impurities in talcum quasi-2D layers","authors":"Gellért Dolecsek, Joel Davidsson, Viktor Ivády","doi":"arxiv-2409.09132","DOIUrl":"https://doi.org/arxiv-2409.09132","url":null,"abstract":"Layered semiconductors have recently emerged as capable host materials for\u0000novel quantum applications ranging from phonics to sensing. Most studies have\u0000focused on artificial layered materials, such as hexagonal boron nitride and\u0000transitional dichalcogenides. Natural layered materials, such as talc and other\u0000silicates, have remained largely unexplored despite their desirable properties,\u0000e.g, wide direct bandgap, low concentration of optically active defects, and\u0000low abundance of nuclear spins. In this article, we carry out an extensive\u0000computational study on pristine and defected talcum layers and discuss their\u0000potential applications. After establishing the properties of bulk talc, we\u0000study the electronic structure, charge states, spin and optical properties of\u0000vacancy defects, metal, metalloid, and non-metallic impurities. We identify\u0000several color centers, electron paramagnetic resonance (EPR) centers, potential\u0000spin quantum bits, and dopants. These findings advance our understanding of\u0000defected talcum layers and point toward potential applications in quantum\u0000technologies.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bamidele Oluwagbenga Onipede, Matthew Metcalf, Nisha Fletcher, Hui Cai
The tuning of the Fermi level in tin telluride, a topological crystalline insulator, is essential for accessing its unique surface states and optimizing its electronic properties for applications such as spintronics and quantum computing. In this study, we demonstrate that the Fermi level in tin telluride can be effectively modulated by controlling the tin concentration during chemical vapor deposition synthesis. By introducing tin-rich conditions, we observed a blue shift in the X-ray photoelectron spectroscopy core-level peaks of both tin and tellurium, indicating an upward shift in the Fermi level. This shift is corroborated by a decrease in work function values measured via ultraviolet photoelectron spectroscopy, confirming the suppression of Sn vacancies. Our findings provide a low-cost, scalable method to achieve tunable Fermi levels in tin telluride, offering a significant advancement in the development of materials with tailored electronic properties for next-generation technological applications.
碲化锡是一种拓扑晶体绝缘体，调谐碲化锡中的费米级对于获得其独特的表面态以及优化其电子特性以应用于自旋电子学和量子计算等领域至关重要。在这项研究中，我们证明了在化学气相沉积合成过程中通过控制锡浓度可以有效地调制碲化锡的费米级。通过引入富锡条件，我们观察到锡和碲的 X 射线光电子能谱核心级峰都发生了蓝移，这表明费米级发生了上移。通过紫外光电子能谱测量到的功函数值的下降也证实了这一移动，从而证实了锡空位的抑制。我们的研究结果提供了一种低成本、可扩展的方法来实现碲化锡的可调费米级，为开发具有定制电子特性的材料提供了重大进展，可用于下一代技术应用。
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Abdulaziz Abogoda, W. A. Shelton, I. Vekhter, J. A. Sauls
We use density functional methods to identify the atomic configurations of H and D atoms trapped by O impurities and embedded in bulk Nb. We calculate the double-well potential for O-H and O-D impurities, wave functions, and tunnel splittings for H and D atoms. Our results are in agreement with those obtained from analysis of heat capacity and neutron scattering measurements on Nb with low concentrations of O-H and O-D.
我们使用密度泛函方法来确定被 O 杂质捕获并嵌入块体铌中的 Hand D 原子的原子构型。我们计算了 O-H 和 O-D 杂质的双阱电势、波函数以及 H 原子和 D 原子的隧道平面。我们的结果与对低浓度 O-H 和 O-D Nb 的热容量分析和中子散射测量结果一致。
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