The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain-walls. We report on the pinning of polarization due to antiphase boundaries in thin films of the multiferroic hexagonal YbFeO$_3$. We have directly resolved the atomic structure of a sharp antiphase boundary (APB) in YbFeO$_3$ thin films using a combination of aberration-corrected scanning transmission electron microscopy (STEM) and total energy calculations based on density-functional theory (DFT). We find the presence of a layer of FeO$_6$ octahedra at the APB that bridge the adjacent domains. STEM imaging shows a reversal in the direction of polarization on moving across the APB, which DFT calculations confirm is structural in nature as the polarization reversal reduces the distortion of the FeO$_6$ octahedral layer at the APB. Such APBs in hexagonal perovskites are expected to serve as domain-wall pinning sites and hinder ferroelectric switching of the domains.
{"title":"Polarization Pinning at an Antiphase Boundary in Multiferroic YbFeO$_3$","authors":"Guodong Ren, Pravan Omprakash, Xin Li, Yu Yun, Arashdeep S. Thind, Xiaoshan Xu, Rohan Mishra","doi":"arxiv-2409.08902","DOIUrl":"https://doi.org/arxiv-2409.08902","url":null,"abstract":"The switching characteristics of ferroelectrics and multiferroics are\u0000influenced by the interaction of topological defects with domain-walls. We\u0000report on the pinning of polarization due to antiphase boundaries in thin films\u0000of the multiferroic hexagonal YbFeO$_3$. We have directly resolved the atomic\u0000structure of a sharp antiphase boundary (APB) in YbFeO$_3$ thin films using a\u0000combination of aberration-corrected scanning transmission electron microscopy\u0000(STEM) and total energy calculations based on density-functional theory (DFT).\u0000We find the presence of a layer of FeO$_6$ octahedra at the APB that bridge the\u0000adjacent domains. STEM imaging shows a reversal in the direction of\u0000polarization on moving across the APB, which DFT calculations confirm is\u0000structural in nature as the polarization reversal reduces the distortion of the\u0000FeO$_6$ octahedral layer at the APB. Such APBs in hexagonal perovskites are\u0000expected to serve as domain-wall pinning sites and hinder ferroelectric\u0000switching of the domains.","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":"142268136","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}
Exploring intrinsic magnetic topological insulators (TIs) for next-generation spintronic devices is still challenging in recent years. Here, we present a theoretical investigation on the electronic, magnetic and topological properties of monolayer (ML) Janus MnBi2TexSe4-x, derived from two trivial magnetic semiconductors ML MnBi2Se4 and MnBi2Te4. Our band structure analysis reveals that two out of the eight Janus structures exhibit band inversion induced by spin-orbit coupling. These structures are confirmed to have nonzero integer Chern numbers, indicating their topological nature. Moreover, the topological state is robust under moderate biaxial strains. Interestingly, applying compressive strain results in a high Chern number of 2 and enhances their magnetic stability at elevated temperatures. Our findings offer an effective strategy to engineer magnetic TI states within the ML MnBi2Te4 family.
近年来，为下一代自旋电子器件探索本征磁性拓扑绝缘体（TIs）仍是一项挑战。在这里，我们介绍了对单层（ML）Janus MnBi2TexSe4-x 的电子、磁性和拓扑特性的理论研究，这些单层（ML）Janus MnBi2TexSe4-x 是由两种三磁半导体 ML MnBi2Se4 和 MnBi2Te4 衍生而来的。我们的能带结构分析表明，在八种 Janus 结构中，有两种表现出了由自旋轨道耦合引起的能带反转。这些结构被证实具有非零点切尔诺数，表明了它们的拓扑性质。此外，拓扑状态在中等双轴应变下也很稳定。有趣的是，施加压缩应变会使它们的切尔数达到 2，并增强它们在高温下的磁稳定性。我们的发现为在 ML MnBi2Te4 家族中设计磁性 TI 状态提供了一种有效的策略。
{"title":"Engineering Quantum Anomalous Hall Effect in Monolayer Janus MnBi2SexTe4-x","authors":"Jiale Chen, Jun Hu","doi":"arxiv-2409.07740","DOIUrl":"https://doi.org/arxiv-2409.07740","url":null,"abstract":"Exploring intrinsic magnetic topological insulators (TIs) for next-generation\u0000spintronic devices is still challenging in recent years. Here, we present a\u0000theoretical investigation on the electronic, magnetic and topological\u0000properties of monolayer (ML) Janus MnBi2TexSe4-x, derived from two trivial\u0000magnetic semiconductors ML MnBi2Se4 and MnBi2Te4. Our band structure analysis\u0000reveals that two out of the eight Janus structures exhibit band inversion\u0000induced by spin-orbit coupling. These structures are confirmed to have nonzero\u0000integer Chern numbers, indicating their topological nature. Moreover, the\u0000topological state is robust under moderate biaxial strains. Interestingly,\u0000applying compressive strain results in a high Chern number of 2 and enhances\u0000their magnetic stability at elevated temperatures. Our findings offer an\u0000effective strategy to engineer magnetic TI states within the ML MnBi2Te4\u0000family.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188161","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}
First-principles calculations were conducted to investigate the structural, electronic and magnetic properties of single Fe atoms and Fe dimers on Cu2N/Cu(100). Upon adsorption of an Fe atom onto Cu2N/Cu(100), robust Fe-N bonds form, resulting in the incorporation of both single Fe atoms and Fe dimers within the surface Cu2N layer. The partial occupancy of Fe-3d orbitals lead to large spin moments on the Fe atoms. Interestingly, both single Fe atoms and Fe dimers exhibit in-plane magnetic anisotropy, with the magnetic anisotropy energy (MAE) of an Fe dimer exceeding twice that of a single Fe atom. This magnetic anisotropy can be attributed to the predominant contribution of the component along the x direction of the spin-orbital coupling Hamiltonian. Additionally, the formation of Fe-Cu dimers may further boost the magnetic anisotropy, as the energy levels of the Fe-3d orbitals are remarkably influenced by the presence of Cu atoms. Our study manifests the significance of uncovering the origin of magnetic anisotropy in engineering the magnetic properties of magnetic nanostructures.
我们通过第一性原理计算研究了单个铁原子和铁二聚体在 Cu2N/Cu(100)上的结构、电子和磁性能。在 Cu2N/Cu(100)上吸附一个铁原子后，会形成牢固的铁键，从而在表面 Cu2N 层中形成单个铁原子和铁二聚体。铁-3d 轨道的部分占据导致铁原子的自旋矩很大。有趣的是，单个铁原子和铁二聚体都表现出平面内的磁各向异性，铁二聚体的磁各向异性能（MAE）超过单个铁原子的两倍。这种磁各向异性可归因于自旋轨道耦合哈密顿的 x 方向分量的主要贡献。此外，Fe-Cu 二聚体的形成可能会进一步增强磁各向异性，因为 Fe-3d 轨道的能级受到 Cu 原子存在的显著影响。我们的研究表明，揭示磁各向异性的起源对于磁性纳米结构的磁特性工程具有重要意义。
{"title":"First-principles study of electronic and magnetic properties of Fe atoms on Cu2N/Cu(100)","authors":"Jiale Chen, Jun Hu","doi":"arxiv-2409.07739","DOIUrl":"https://doi.org/arxiv-2409.07739","url":null,"abstract":"First-principles calculations were conducted to investigate the structural,\u0000electronic and magnetic properties of single Fe atoms and Fe dimers on\u0000Cu2N/Cu(100). Upon adsorption of an Fe atom onto Cu2N/Cu(100), robust Fe-N\u0000bonds form, resulting in the incorporation of both single Fe atoms and Fe\u0000dimers within the surface Cu2N layer. The partial occupancy of Fe-3d orbitals\u0000lead to large spin moments on the Fe atoms. Interestingly, both single Fe atoms\u0000and Fe dimers exhibit in-plane magnetic anisotropy, with the magnetic\u0000anisotropy energy (MAE) of an Fe dimer exceeding twice that of a single Fe\u0000atom. This magnetic anisotropy can be attributed to the predominant\u0000contribution of the component along the x direction of the spin-orbital\u0000coupling Hamiltonian. Additionally, the formation of Fe-Cu dimers may further\u0000boost the magnetic anisotropy, as the energy levels of the Fe-3d orbitals are\u0000remarkably influenced by the presence of Cu atoms. Our study manifests the\u0000significance of uncovering the origin of magnetic anisotropy in engineering the\u0000magnetic properties of magnetic nanostructures.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188166","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}
One long-standing and crucial issues in the study of quasicrystals has been to identify the physical properties characteristic of quasicrystals. The large positive temperature coefficient of thermal conductivity at temperatures above room temperature, which has been observed in several quasicrystals, is one such characteristic property. Here, we show that this is indeed a very distinct property of quasicrystals through analysis using a large physical property database "Starrydata". In fact, several quasicrystals ranked nearly first among more than 10,000 samples of various materials (metallic alloys, semiconductors, ceramics, etc.) in terms of the magnitude of the positive temperature coefficient of thermal conductivity. This unique property makes quasicrystals ideal for use in composite thermal diodes. We searched the database for the most suitable materials that can be combined with quasicrystals to create high-performance composite thermal diodes. Analytical calculations using a simple one-dimensional model showed that by selecting the optimal material, a thermal rectification ratio of 3.2 can be obtained. Heat transfer simulations based on the finite element method confirmed that this can be achieved under realistic conditions. This is the highest value of the thermal rectification ratio reported to date for this type of thermal diode.
{"title":"Large-scale database analysis of anomalous thermal conductivity of quasicrystals and its application to thermal diodes","authors":"Takashi Kurono, Jinjia Zhang, Yasushi Kamimura, Keiichi Edagawa","doi":"arxiv-2409.07735","DOIUrl":"https://doi.org/arxiv-2409.07735","url":null,"abstract":"One long-standing and crucial issues in the study of quasicrystals has been\u0000to identify the physical properties characteristic of quasicrystals. The large\u0000positive temperature coefficient of thermal conductivity at temperatures above\u0000room temperature, which has been observed in several quasicrystals, is one such\u0000characteristic property. Here, we show that this is indeed a very distinct\u0000property of quasicrystals through analysis using a large physical property\u0000database \"Starrydata\". In fact, several quasicrystals ranked nearly first among\u0000more than 10,000 samples of various materials (metallic alloys, semiconductors,\u0000ceramics, etc.) in terms of the magnitude of the positive temperature\u0000coefficient of thermal conductivity. This unique property makes quasicrystals\u0000ideal for use in composite thermal diodes. We searched the database for the\u0000most suitable materials that can be combined with quasicrystals to create\u0000high-performance composite thermal diodes. Analytical calculations using a\u0000simple one-dimensional model showed that by selecting the optimal material, a\u0000thermal rectification ratio of 3.2 can be obtained. Heat transfer simulations\u0000based on the finite element method confirmed that this can be achieved under\u0000realistic conditions. This is the highest value of the thermal rectification\u0000ratio reported to date for this type of thermal diode.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188162","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}
Xiaosong Bai, Yan Wang, Wenwen Yang, Qiunan Xu, Wenjian Liu
Magnetic Weyl semimetals (WSM) have recently attracted much attention due to their potential in realizing strong anomalous Hall effects. Yet, how to design such systems remains unclear. Based on first-principles calculations, we show here that the ferromagnetic half-metallic compound In$_2$CoSe$_4$ has several pairs of Weyl points and is hence a good candidate for magnetic WSM. These Weyl points would approach the Fermi level gradually as the Hubbard $U$ increases, and finally disappear after a critical value $U_c$. The range of the Hubbard $U$ that can realize the magnetic WSM state can be expanded by pressure, manifesting the practical utility of the present prediction. Moreover, by generating two surface terminations at Co or In atom after cleaving the compound at the Co-Se bonds, the nontrivial Fermi arcs connecting one pair of Weyl points with opposite chirality are discovered in surface states. Furthermore, it is possible to observe the nontrivial surface state experimentally, e.g., angle-resolved photoemission spectroscopy (ARPES) measurements. As such, the present findings imply strongly a new magnetic WSM which may host a large anomalous Hall conductivity.
{"title":"Magnetic topological Weyl fermions in half-metallic In$_2$CoSe$_4$","authors":"Xiaosong Bai, Yan Wang, Wenwen Yang, Qiunan Xu, Wenjian Liu","doi":"arxiv-2409.07727","DOIUrl":"https://doi.org/arxiv-2409.07727","url":null,"abstract":"Magnetic Weyl semimetals (WSM) have recently attracted much attention due to\u0000their potential in realizing strong anomalous Hall effects. Yet, how to design\u0000such systems remains unclear. Based on first-principles calculations, we show\u0000here that the ferromagnetic half-metallic compound In$_2$CoSe$_4$ has several\u0000pairs of Weyl points and is hence a good candidate for magnetic WSM. These Weyl\u0000points would approach the Fermi level gradually as the Hubbard $U$ increases,\u0000and finally disappear after a critical value $U_c$. The range of the Hubbard\u0000$U$ that can realize the magnetic WSM state can be expanded by pressure,\u0000manifesting the practical utility of the present prediction. Moreover, by\u0000generating two surface terminations at Co or In atom after cleaving the\u0000compound at the Co-Se bonds, the nontrivial Fermi arcs connecting one pair of\u0000Weyl points with opposite chirality are discovered in surface states.\u0000Furthermore, it is possible to observe the nontrivial surface state\u0000experimentally, e.g., angle-resolved photoemission spectroscopy (ARPES)\u0000measurements. As such, the present findings imply strongly a new magnetic WSM\u0000which may host a large anomalous Hall conductivity.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188163","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}
Christopher C. Price, Yansong Li, Guanyu Zhou, Rehan Younas, Spencer S. Zeng, Tim H. Scanlon, Jason M. Munro, Christopher L. Hinkle
Solving for the complex conditions of materials synthesis and processing requires analyzing information gathered from multiple modes of characterization. Currently, quantitative information is extracted serially with manual tools and intuition, constraining the feedback cycle for process optimization. We use machine learning to automate and generalize feature extraction for in-situ reflection high-energy electron diffraction (RHEED) data to establish quantitatively predictive relationships in small sets ($sim$10) of expert-labeled data, and apply these to save significant time on subsequent epitaxially grown samples. The fidelity of these relationships is tested on a representative material system ($W_{1-x}V_xSe2$ growth on c-plane sapphire substrate (0001)) at two stages of synthesis with two aims: 1) predicting the grain alignment of the deposited film from the pre-growth substrate surface data, and 2) estimating the vanadium (V) dopant concentration using in-situ RHEED as a proxy for ex-situ methods (e.g. x-ray photoelectron spectroscopy). Both tasks are accomplished using the same set of materials agnostic core features, eliminating the need to retrain for specific systems and leading to a potential 80% time saving over a 100 sample synthesis campaign. These predictions provide guidance for recipe adjustments to avoid doomed trials, reduce follow-on characterization, and improve control resolution for materials synthesis, ultimately accelerating materials discovery and commercial scale-up.
要解决材料合成和加工的复杂条件，就必须分析从多种表征模式中收集到的信息。目前，定量信息是通过手动工具和直觉连续提取的，这限制了工艺优化的反馈周期。我们利用机器学习来自动和通用原位反射高能电子衍射（RHEED）数据的特征提取，在专家标记的小型数据集中（$sim$10）建立定量预测关系，并将这些关系应用于后续片晶生长样品，从而节省大量时间。我们在两个合成阶段的代表性材料系统（在 c 平面蓝宝石衬底 (0001) 上生长的 $W_{1-x}V_xSe2$）上测试了这些关系的保真度，目的有两个：1) 根据生长前基底表面数据预测沉积薄膜的晶粒排列，以及 2) 使用原位 RHEED 代替原位方法（例如 x 射线光电子能谱）估算钒（V）掺杂浓度。这两项任务都是使用同一套材料无关核心特征完成的，无需针对特定系统进行重新训练，从而在 100 个样品的合成过程中节省 80% 的时间。这些预测为配方调整提供了指导，以避免注定失败的试验，减少后续表征，提高材料合成的控制分辨率，最终加速材料发现和商业放大。
{"title":"Predicting and Accelerating Nanomaterials Synthesis Using Machine Learning Featurization","authors":"Christopher C. Price, Yansong Li, Guanyu Zhou, Rehan Younas, Spencer S. Zeng, Tim H. Scanlon, Jason M. Munro, Christopher L. Hinkle","doi":"arxiv-2409.08054","DOIUrl":"https://doi.org/arxiv-2409.08054","url":null,"abstract":"Solving for the complex conditions of materials synthesis and processing\u0000requires analyzing information gathered from multiple modes of\u0000characterization. Currently, quantitative information is extracted serially\u0000with manual tools and intuition, constraining the feedback cycle for process\u0000optimization. We use machine learning to automate and generalize feature\u0000extraction for in-situ reflection high-energy electron diffraction (RHEED) data\u0000to establish quantitatively predictive relationships in small sets ($sim$10)\u0000of expert-labeled data, and apply these to save significant time on subsequent\u0000epitaxially grown samples. The fidelity of these relationships is tested on a\u0000representative material system ($W_{1-x}V_xSe2$ growth on c-plane sapphire\u0000substrate (0001)) at two stages of synthesis with two aims: 1) predicting the\u0000grain alignment of the deposited film from the pre-growth substrate surface\u0000data, and 2) estimating the vanadium (V) dopant concentration using in-situ\u0000RHEED as a proxy for ex-situ methods (e.g. x-ray photoelectron spectroscopy).\u0000Both tasks are accomplished using the same set of materials agnostic core\u0000features, eliminating the need to retrain for specific systems and leading to a\u0000potential 80% time saving over a 100 sample synthesis campaign. These\u0000predictions provide guidance for recipe adjustments to avoid doomed trials,\u0000reduce follow-on characterization, and improve control resolution for materials\u0000synthesis, ultimately accelerating materials discovery and commercial scale-up.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188156","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}
Niccolò Bancone, Rosangela Santalucia, Stefano Pantaleone, Piero Ugliengo, Lorenzo Mino, Albert Rimola, Marta Corno
Understanding the interaction between hydrogen cyanide (HCN) and silicate surfaces is crucial for elucidating the prebiotic processes occurring on interstellar grain cores, as well as in cometary and meteoritic matrices. In this study, we characterized the adsorption features of HCN on crystalline forsterite (Mg2SiO4) surfaces, one of the most abundant cosmic silicates, by combining experimental infrared spectra at low temperatures (100-150 K) with periodic DFT simulations. Results showed the coexistence of both molecular and dissociative HCN adsorption complexes as a function of the considered forsterite crystalline face. Molecular adsorptions dominate on the most stable surfaces, while dissociative adsorptions occur predominantly on surfaces of lower stability, catalyzed by the enhanced Lewis acid-base behavior of surface-exposed Mg2+-O2- ion pairs. On the whole set of adsorption cases, harmonic frequency calculations were carried out and compared with the experimental infrared bands. To disentangle each vibrational mode contributing to the experimental broad bands, we run a best non-linear fit between the predicted set of frequencies and the experimental bands. The outcome of this procedure allowed us to: i) deconvolute the experimental IR spectrum by assigning computed normal modes of vibrations to the main features of each band; ii) reveal which crystal faces are responsible of the largest contribution to the adsorbate vibrational bands, giving information about the morphology of the samples. The present straigthforward procedure is quite general and of broad interest in the fine characterization of the infrared spectra of adsorbates on complex inorganic material surfaces.
{"title":"Unraveling the Interface Chemistry between HCN and Cosmic Silicates by the Interplay of Infrared Spectroscopy and Quantum Chemical Modeling","authors":"Niccolò Bancone, Rosangela Santalucia, Stefano Pantaleone, Piero Ugliengo, Lorenzo Mino, Albert Rimola, Marta Corno","doi":"arxiv-2409.08074","DOIUrl":"https://doi.org/arxiv-2409.08074","url":null,"abstract":"Understanding the interaction between hydrogen cyanide (HCN) and silicate\u0000surfaces is crucial for elucidating the prebiotic processes occurring on\u0000interstellar grain cores, as well as in cometary and meteoritic matrices. In\u0000this study, we characterized the adsorption features of HCN on crystalline\u0000forsterite (Mg2SiO4) surfaces, one of the most abundant cosmic silicates, by\u0000combining experimental infrared spectra at low temperatures (100-150 K) with\u0000periodic DFT simulations. Results showed the coexistence of both molecular and\u0000dissociative HCN adsorption complexes as a function of the considered\u0000forsterite crystalline face. Molecular adsorptions dominate on the most stable\u0000surfaces, while dissociative adsorptions occur predominantly on surfaces of\u0000lower stability, catalyzed by the enhanced Lewis acid-base behavior of\u0000surface-exposed Mg2+-O2- ion pairs. On the whole set of adsorption cases,\u0000harmonic frequency calculations were carried out and compared with the\u0000experimental infrared bands. To disentangle each vibrational mode contributing\u0000to the experimental broad bands, we run a best non-linear fit between the\u0000predicted set of frequencies and the experimental bands. The outcome of this\u0000procedure allowed us to: i) deconvolute the experimental IR spectrum by\u0000assigning computed normal modes of vibrations to the main features of each\u0000band; ii) reveal which crystal faces are responsible of the largest\u0000contribution to the adsorbate vibrational bands, giving information about the\u0000morphology of the samples. The present straigthforward procedure is quite\u0000general and of broad interest in the fine characterization of the infrared\u0000spectra of adsorbates on complex inorganic material surfaces.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188155","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}
Jaesun Kim, Jisu Kim, Jaehoon Kim, Jiho Lee, Yutack Park, Youngho Kang, Seungwu Han
Machine learning interatomic potentials (MLIPs) are used to estimate potential energy surfaces (PES) from ab initio calculations, providing near quantum-level accuracy with reduced computational costs. However, the high cost of assembling high-fidelity databases hampers the application of MLIPs to systems that require high chemical accuracy. Utilizing an equivariant graph neural network, we present an MLIP framework that trains on multi-fidelity databases simultaneously. This approach enables the accurate learning of high-fidelity PES with minimal high-fidelity data. We test this framework on the Li$_6$PS$_5$Cl and In$_x$Ga$_{1-x}$N systems. The computational results indicate that geometric and compositional spaces not covered by the high-fidelity meta-gradient generalized approximation (meta-GGA) database can be effectively inferred from low-fidelity GGA data, thus enhancing accuracy and molecular dynamics stability. We also develop a general-purpose MLIP that utilizes both GGA and meta-GGA data from the Materials Project, significantly enhancing MLIP performance for high-accuracy tasks such as predicting energies above hull for crystals in general. Furthermore, we demonstrate that the present multi-fidelity learning is more effective than transfer learning or $Delta$-learning an d that it can also be applied to learn higher-fidelity up to the coupled-cluster level. We believe this methodology holds promise for creating highly accurate bespoke or universal MLIPs by effectively expanding the high-fidelity dataset.
{"title":"Data-efficient multi-fidelity training for high-fidelity machine learning interatomic potentials","authors":"Jaesun Kim, Jisu Kim, Jaehoon Kim, Jiho Lee, Yutack Park, Youngho Kang, Seungwu Han","doi":"arxiv-2409.07947","DOIUrl":"https://doi.org/arxiv-2409.07947","url":null,"abstract":"Machine learning interatomic potentials (MLIPs) are used to estimate\u0000potential energy surfaces (PES) from ab initio calculations, providing near\u0000quantum-level accuracy with reduced computational costs. However, the high cost\u0000of assembling high-fidelity databases hampers the application of MLIPs to\u0000systems that require high chemical accuracy. Utilizing an equivariant graph\u0000neural network, we present an MLIP framework that trains on multi-fidelity\u0000databases simultaneously. This approach enables the accurate learning of\u0000high-fidelity PES with minimal high-fidelity data. We test this framework on\u0000the Li$_6$PS$_5$Cl and In$_x$Ga$_{1-x}$N systems. The computational results\u0000indicate that geometric and compositional spaces not covered by the\u0000high-fidelity meta-gradient generalized approximation (meta-GGA) database can\u0000be effectively inferred from low-fidelity GGA data, thus enhancing accuracy and\u0000molecular dynamics stability. We also develop a general-purpose MLIP that\u0000utilizes both GGA and meta-GGA data from the Materials Project, significantly\u0000enhancing MLIP performance for high-accuracy tasks such as predicting energies\u0000above hull for crystals in general. Furthermore, we demonstrate that the\u0000present multi-fidelity learning is more effective than transfer learning or\u0000$Delta$-learning an d that it can also be applied to learn higher-fidelity up\u0000to the coupled-cluster level. We believe this methodology holds promise for\u0000creating highly accurate bespoke or universal MLIPs by effectively expanding\u0000the high-fidelity dataset.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224494","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}
A. Nonato, Juan S. Rodríguez-Hernández, D. S. Abreu, C. C. S. Soares, Mayra A. P. Gómez, Alberto García-Fernández, María A. Señarís-Rodríguez, Manuel Sánchez andújar, A. P. Ayala, C. W. A. Paschoal, Rosivaldo Xavier da Silva
Hybrid halide perovskites (HHPs) have attracted significant attention due to their remarkable optoelectronic properties that combine the advantages of low cost-effective fabrication methods of organic-inorganic materials. Notably, low-dimensional hybrid halide perovskites including two-dimensional (2D) layers and one-dimensional (1D) chains, are recognized for their superior stability and moisture resistance, making them highly appealing for practical applications. Particularly, DMAPbI3 has attracted attention due to other interesting behaviors and properties, such as thermally induced order-disorder processes, dielectric transition, and cooperative electric ordering of DMA dipole moments. In this paper, we investigated the interplay between low-temperature SPT undergone by the low-dimensional (1D) hybrid halide perovskite-like material DMAPbI3 and its optoelectronic properties. Our approach combines synchrotron X-ray powder diffraction, Raman spectroscopy, thermo-microscopy, differential scanning calorimetry (DSC), and photoluminescence (PL) techniques. Temperature-dependent Synchrotron powder diffraction and Raman Spectroscopy reveal that the modes associated with I-Pb-I and DMA+ ion play a crucial role in the order-disorder SPT in DMAPbI3. The reversible SPT modifies its optoelectronic properties, notably affecting its thermochromic behavior and PL emission. The origin of the PL phenomenon is associated to self-trapped excitons (STEs), which are allowed due to a strong electron-phonon coupling quantified by the Huang-Rhys factor (S = 97+-1). Notably, we identify the longitudinal optical (LO) phonon mode at 84 cm-1 which plays a significant role in electron-phonon interaction. Our results show these STEs not only intensify the PL spectra at lower temperatures but also induce a shift in the color emission, transforming it from a light orange-red to an intense bright strong red.
{"title":"Strong Electron-Phonon Coupling and Lattice Dynamics in One-Dimensional [(CH3)2NH2]PbI3 Hybrid Perovskite","authors":"A. Nonato, Juan S. Rodríguez-Hernández, D. S. Abreu, C. C. S. Soares, Mayra A. P. Gómez, Alberto García-Fernández, María A. Señarís-Rodríguez, Manuel Sánchez andújar, A. P. Ayala, C. W. A. Paschoal, Rosivaldo Xavier da Silva","doi":"arxiv-2409.08259","DOIUrl":"https://doi.org/arxiv-2409.08259","url":null,"abstract":"Hybrid halide perovskites (HHPs) have attracted significant attention due to\u0000their remarkable optoelectronic properties that combine the advantages of low\u0000cost-effective fabrication methods of organic-inorganic materials. Notably,\u0000low-dimensional hybrid halide perovskites including two-dimensional (2D) layers\u0000and one-dimensional (1D) chains, are recognized for their superior stability\u0000and moisture resistance, making them highly appealing for practical\u0000applications. Particularly, DMAPbI3 has attracted attention due to other\u0000interesting behaviors and properties, such as thermally induced order-disorder\u0000processes, dielectric transition, and cooperative electric ordering of DMA\u0000dipole moments. In this paper, we investigated the interplay between\u0000low-temperature SPT undergone by the low-dimensional (1D) hybrid halide\u0000perovskite-like material DMAPbI3 and its optoelectronic properties. Our\u0000approach combines synchrotron X-ray powder diffraction, Raman spectroscopy,\u0000thermo-microscopy, differential scanning calorimetry (DSC), and\u0000photoluminescence (PL) techniques. Temperature-dependent Synchrotron powder\u0000diffraction and Raman Spectroscopy reveal that the modes associated with I-Pb-I\u0000and DMA+ ion play a crucial role in the order-disorder SPT in DMAPbI3. The\u0000reversible SPT modifies its optoelectronic properties, notably affecting its\u0000thermochromic behavior and PL emission. The origin of the PL phenomenon is\u0000associated to self-trapped excitons (STEs), which are allowed due to a strong\u0000electron-phonon coupling quantified by the Huang-Rhys factor (S = 97+-1).\u0000Notably, we identify the longitudinal optical (LO) phonon mode at 84 cm-1 which\u0000plays a significant role in electron-phonon interaction. Our results show these\u0000STEs not only intensify the PL spectra at lower temperatures but also induce a\u0000shift in the color emission, transforming it from a light orange-red to an\u0000intense bright strong red.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224519","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}
Yueqiao Qu, Yu Liao, Zhixiang Wang, Liang Liu, Gang Yao
Controllable magnetization in atomically thin two-dimensional magnets is highly desirable for developing spintronics. For FeSe monolayer, its magnetic ground state is not yet fully understood, and the potential in constructing high-speed and advanced devices remains unknown. Using density functional theory calculations, we confirm the spin ordering of monolayer FeSe to be dimer texture. With Fluorine (F) adsorption (F/FeSe), the system exhibits a coverage dependent magnetic anisotropy and multiferroicity which can be attributable to the Jahn-Teller effect, being the benefit to potential spintronic applications. Intriguingly, an inherent coupling between magnetism and ferroelasticity in the most energetically favorable F/FeSe system is proposed. Our study thus not only provides a promising way to control the spintronic properties and construct multiferroics, but also renders F/FeSe an ideal platform for magnetism studies and practical high-performance multifunctional devices.
{"title":"Controllable magnetic anisotropy and ferroelasticity in superconducting FeSe monolayer with surface fluorine adsorption","authors":"Yueqiao Qu, Yu Liao, Zhixiang Wang, Liang Liu, Gang Yao","doi":"arxiv-2409.07910","DOIUrl":"https://doi.org/arxiv-2409.07910","url":null,"abstract":"Controllable magnetization in atomically thin two-dimensional magnets is\u0000highly desirable for developing spintronics. For FeSe monolayer, its magnetic\u0000ground state is not yet fully understood, and the potential in constructing\u0000high-speed and advanced devices remains unknown. Using density functional\u0000theory calculations, we confirm the spin ordering of monolayer FeSe to be dimer\u0000texture. With Fluorine (F) adsorption (F/FeSe), the system exhibits a coverage\u0000dependent magnetic anisotropy and multiferroicity which can be attributable to\u0000the Jahn-Teller effect, being the benefit to potential spintronic applications.\u0000Intriguingly, an inherent coupling between magnetism and ferroelasticity in the\u0000most energetically favorable F/FeSe system is proposed. Our study thus not only\u0000provides a promising way to control the spintronic properties and construct\u0000multiferroics, but also renders F/FeSe an ideal platform for magnetism studies\u0000and practical high-performance multifunctional devices.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188159","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}
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