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First-principles calculations on structural stability and electronic properties of nitrogen-doped lutetium hydrides under pressure

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Physical Review Research 2023年第4期5卷 043238-043238页

作者： Xiaokuan Hao Xudong Wei Hanyu Liu Xiaoxu Song Rongxin Sun Guoying Gao Yongjun Tian Center for High Pressure Science (CHiPS) State Key Laboratory of Metastable Materials Science and Technology Yanshan University Qinhuangdao Hebei 066004 China Key Laboratory of Material Simulation Methods and Software of Ministry of Education College of Physics Jilin University Changchun 130012 China Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education) International Center of Future Science Jilin University Changchun 130012 China

Since the discovery of superconductivity, the realization of room-temperature superconductivity has been the long dream of mankind. Recently, it has been reported that nitrogen-doped lutetium hydride has room-temperature superconductivity at near-ambient conditions. However, there is no solid evidence of such tantalizing superconductivity in nitrogen-doped lutetium hydride synthesized by follow-up experiments. The compositions and crystal structures of the nitrogen-doped lutetium hydride are still unclear. Therefore, we here systematically study the structural stability and electronic properties of Fm3¯m LuH3 and N-doped Fm3¯m LuH3, such as 1, 2, 3, 4, and 8% N, by first-principles calculations. Our further electronic properties calculations show that all the simulated Lu-N-H ternary compounds are metallic, except for a semiconducting phase of Lu4H11N (LuH2.75N0.25). Remarkably, the contribution of the H atoms to the electronic density of states at the Fermi level could be tuned by the increasing N concentration. Electron-phonon coupling calculations also show that both Fm3¯m LuH3 and Pm3¯m Lu4H11N are superconducting with critical temperature Tc's of 23 and 32 K at 24 and 60 GPa, respectively. Our current results suggest that LuH3 and N-doped LuH3 could be potential superconductors only at high pressure, while the estimated Tc values are much lower than room temperature.

关键词： Density of states First-principles calculations Superconductivity Crystal structures

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Computational prediction of ideal strength for a material

arXiv

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arXiv 2023年

作者： Wang, Zixun Wang, Xingyu Song, Xianqi Zhang, Xinxin Liu, Hanyu Zhang, Miao Key Laboratory of Material Simulation Methods and Software Ministry of Education State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun130012 China Department of Physics School of Sciences Beihua University Jilin132013 China Department of Science Shenyang University of Chemical Technology Shenyang110142 China

The ideal strength is crucial for predicting material behavior under extreme conditions, which can provide insights into material limits, guide design and engineer for enhanced performance and durability. In this work, we present a method within an allows for the estimation of tensile, shear, and indentation strengths in any crystallographic direction or plane. We have examined the strain-stress relationships of several well-known structures and compared our findings with previous work, demonstrating the effectiveness of our approach. Moreover, we performed extensive investigations into the indentation strength of hexagonal WC, β-SiC, and MgAl2O4. The current study uncovers the modes of structural deformation and the underlying atomistic mechanisms. The insights gained from this study have significant implications for the further exploration and design of superhard materials. © 2023, CC BY.

关键词： Tensile strength

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Nonlocal free-energy density functional for warm dense matter

arXiv

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arXiv 2024年

作者： Ma, Cheng Chen, Min Xie, Yu Xu, Qiang Mi, Wenhui Wang, Yanchao Ma, Yanming Key Laboratory of Material Simulation Methods & Software Ministry of Education College of Physics Jilin University Changchun130012 China State Key Lab of Superhard Materials College of Physics Jilin University Changchun130012 China International Center of Future Science Jilin University Changchun130012 China

Finite-temperature orbital-free density functional theory (FT-OFDFT) holds significant promise for simulating warm dense matter due to its favorable scaling with both system size and temperature. However, the lack of the numerically accurate and transferable noninteracting free energy functionals results in a limit on the application of FT-OFDFT for warm dense matter simulations. Here, a nonlocal free energy functional, named XWMF, was derived by line integrals for FT-OFDFT simulations. Particularly, a designed integral path, wherein the electronic density varies from uniform to inhomogeneous, was employed to accurately describe deviations in response behavior from the uniform electron gas. The XWMF has been benchmarked by a range of warm dense matter systems including the Si, Al, H, He, and H-He mixture. The simulated results demonstrate that FT-OFDFT within XWMF achieves remarkable performance for accuracy and numerical stability. It is worth noting that XWMF exhibits a low computational cost for large-scale ab initio simulations, offering exciting opportunities for the realistic simulations of warm dense matter systems covering a broad range of temperatures and pressures. Copyright © 2024, The Authors. All rights reserved.

关键词： Free energy

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Zeeman spin splittings with persistent spin textures in antiferromagnetic semiconductors

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Physical Review B 2023年第12期108卷 125108-125108页

作者： Xinran Liu Hong Jian Zhao Laurent Bellaiche Yanming Ma Key Laboratory of Material Simulation Methods and Software of Ministry of Education College of Physics Jilin University Changchun 130012 China Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education) College of Physics Jilin University Changchun 130012 China International Center of Future Science Jilin University Changchun 130012 China Physics Department and Institute for Nanoscience and Engineering University of Arkansas Fayetteville Arkansas 72701 USA State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun 130012 China

Realizing sizable Zeeman spin splittings (ZSSs) with persistent spin textures (PSTs) in semiconductors is promising for the design of high-performance spintronic devices. The ZSSs of this kind have long been known in ferromagnetic semiconductors, while whether antiferromagnetic semiconductors—much more plenteous than ferromagnetic semiconductors—can host an analogous effect remains elusive. Here, we show that such ZSSs can occur in antiferromagnetic semiconductors. By symmetry analysis, we find 12 magnetic point groups that can host ZSSs and PSTs, providing theoretical guidelines for screening the corresponding antiferromagnets. Our first-principles calculations further confirm CaTcO3 as an antiferromagnetic semiconductor showcasing ZSSs that are sizable (tens of meV), possibly controllable by a magnetic field, and accompanied with PSTs. Our work thus may open a route towards the application of antiferromagnetic semiconductors in spintronics.

关键词： Dresselhaus coupling Magnetoelectric effect Rashba coupling Zeeman effect Antiferromagnets Multiferroics Perovskites First-principles calculations

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Layer Hall Detection of the Néel Vector in Centrosymmetric Magnetoelectric Antiferromagnets

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Physical Review Letters 2024年第9期133卷 096803页

作者： L. L. Tao Qin Zhang Huinan Li Hong Jian Zhao Xianjie Wang Bo Song Evgeny Y. Tsymbal Laurent Bellaiche School of Physics Key Laboratory of Material Simulation Methods and Software of Ministry of Education College of Physics International Center of Future Science National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience Smart Ferroic Materials Center Physics Department and Institute for Nanoscience and Engineering Department of Materials Science and Engineering Tel Aviv University Ramat Aviv Tel Aviv 6997801 Israel

The efficient detection of the Néel vector in antiferromagnets is one of the prerequisites toward antiferromagnetic spintronic devices and remains a challenging problem. Here, we propose that the layer Hall effect can be used to efficiently detect the Néel vector in centrosymmetric magnetoelectric antiferromagnets. Thanks to the robust surface magnetization of magnetoelectric antiferromagnets, the combination of sizable exchange field and an applied electric field results in the layer-locked spin-polarized band edges. Moreover, the Berry curvature can be engineered efficiently by an electric field, which consequently gives rise to the layer-locked Berry curvature responsible for the layer Hall effect. Importantly, it is demonstrated that the layer Hall conductivity strongly depends on the Néel vector orientation and exhibits rich electromagnetic responses, which can be used to detect the Néel vector reversal. Based on density functional theory calculations, we exemplify those phenomena in the prototypical Cr2O3 compound. A complete list of the magnetic point groups sustaining the layer Hall effect is presented, aiding the search for realistic materials. Our work proposes a novel approach to detect the Néel vector and holds great promise for antiferromagnetic spintronic applications.

关键词： Anomalous Hall effect Magnetoelectric effect Transport phenomena Antiferromagnets Multiferroics First-principles calculations k dot p method

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Theoretical Design of Superhard Twinned Bc2n

SSRN

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SSRN 2023年

作者： Min, Nan Liang, Hui Chen, Hao Song, Xianqi Zhou, Dan Li, Quan State Key Lab of Superhard Materials Key Laboratory of Material Simulation Methods & Software Ministry of Education College of Physics Jilin University Changchun130012 China International Center of Future Science Jilin University Changchun130012 China School of Physics Changchun University of Science and Technology Changchun130022 China

BC2N is an ideal combination of diamond and boron nitride and is expected to exhibit better mechanical properties and thermal stability than boron nitride and diamond, respectively. Recent studies raise exciting prospects of building coherent nanotwinned boundaries to improve performance of ceramics. Herein, we developed a systematic method to construct twin structures of BC2N. The newly identified nanotwinned BC2N variant (τ-BC2N) exhibits better energetic stability and higher mechanical strength than single-crystal BC2N, attributed to the optimized bonding behavior and crystal orientations induced via twinning. The simulated X-ray diffraction patterns of τ-BC2N match those reported in previous experimental data. The nanotwinned BC2N displays superior Vickers hardness of ~140 GPa, surpassing that of diamond. The computationally tailored approach and results obtained by twin-strengthening strategies offer powerful insights for the rational design and functional optimization of nanotwinned boron–carbon–nitrogen compounds containing intricate multiatomic constituents and structures. © 2023, The Authors. All rights reserved.

关键词： III-V semiconductors

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Monolayer ThSi2N4: An indirect-gap semiconductor with ultra-high carrier mobility

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Physical Review B 2023年第20期108卷 205427-205427页

作者： Cheng Lu Chuyan Cui Jingning Zuo Hongxia Zhong Shi He Wei Dai Xin Zhong School of Mathematics and Physics China University of Geosciences (Wuhan) Wuhan 430074 China School of Mathematics and Physics Jingchu University of Technology Jingmen 448000 China Key Laboratory of Materials Simulation Methods & Software of Ministry of Education College of Physics Jilin University Changchun 130012 China

The recently synthesized MoSi2N4 monolayer [Science 369, 670 (2020)] exhibit outstanding environmental stability, moderate band gap, and excellent mechanical properties, which opens up a new avenue for the explorations of two-dimensional (2D) MA2Z4 materials. Inspired by this finding, we perform comprehensive structural predictions of MSi2N4 monolayers with lanthanide and actinide metals at the M site. Using the CALYPSO structural search method and first-principles calculations, we identify seven MSi2N4 monolayers with robust ambient stabilities, four of which are metals (M = Tm, Lu, Pa, Np) and three are semiconductors (M = Ce, Th, U). Of particular interest is the ThSi2N4 monolayer, which is an indirect-gap semiconductor with ultra-high electron mobility of 14384 cm2V−1s−1. Our results enrich the 2D MA2Z4 family and offer insights into the design and synthesis of novel multifunctional materials.

关键词： Electrical properties 2-dimensional systems Crystal structures First-principles calculations

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Creating cyclo-N5+ cation and assembling N5+N5− salt via electronegativity co-matching in tailored ionic compounds

arXiv

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arXiv 2024年

作者： Zhang, Bi Xin, Yu Xu, Meiling Zhang, Yiming Li, Yinwei Wang, Yanchao Chen, Changfeng Laboratory of Quantum Functional Materials Design and Application School of Physics and Electronic Engineering Jiangsu Normal University Xuzhou221116 China Key Laboratory of Material Simulation Methods and Software Ministry of Education State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun130012 China Department of Physics and Astronomy University of Nevada Las VegasNV89154 United States

The recent discovery of crystalline pentazolates marks a major advance in polynitrogen science and raises prospects of making the long-touted potent propellant N5+N5− salt. However, despite the synthesis of cycloN5− anion in pentazolates, counter cation cyclo-N5+ remains elusive due to the strong oxidizing power of pentazole ion;moreover, pure N5+N5− salt is known to be unstable. Here, we devise a new strategy for making rare cyclo-N5+ cation and assembling the long-sought N5+N5− salt in tailored ionic compounds, wherein the negative/positive host ions act as oxidizing/reducing agents to form cyclo-N5+/N5− species. This strategy is implemented via an advanced computational crystal structure search, which identifies XN5N5F (X = Li, Na, K) compounds that stabilize at high pressures and remain viable at ambient pressure-temperature conditions based on ab initio molecular dynamics simulations. This finding opens an avenue for creating and stabilizing N5+N5− salt assembly in ionic compounds, where cyclo-N5 species are oxidized/reduced via co-matching with host ions of high/low electronegativity. The present results demonstrate novel polynitrogen chemistry, and these findings offer new insights and prospects in the design and synthesis of diverse chemical species that exhibit unusual charge states, bonding structures, and superior functionality. Copyright © 2024, The Authors. All rights reserved.

关键词： Electronegativity

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Data-driven design of high-temperature superconductivity among ternary hydrides under pressure

arXiv

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arXiv 2024年

作者： Jiang, Bowen Luo, Xiaoshan Iitaka, Toshiaki Sun, Ying Zhong, Xin Lv, Jian Xie, Yu Ma, Yanming Liu, Hanyu Key Laboratory of Material Simulation Methods and Software of Ministry of Education College of Physics Jilin University Changchun130012 China State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun130012 China International Center of Future Science Jilin University Changchun130012 China Discrete Event Simulation Research Team RIKEN Center for Computational Science 2-1 Hirosawa Saitama Wako351-0198 Japan

Recently, ternary clathrate hydrides are promising candidates for high-temperature superconductor. However, it is a formidable challenge to effectively hunt high-temperature superconductivity among multinary hydrides due to the expensive computational cost associated with large unit cells and huge stoichiometric choices. Here we present an efficiently data-driven strategy, including generated clathrate frameworks, the quick estimation of stability for each framework and superconducting critical temperature (Tc) for each hydride structure, to accelerate the discovery of high-temperature superconducting hydrides. Our strategy was initialized with more than one million input structures via zeolite databases and our generated dataset. As a result, such a strategy hitherto uncovered 14 prototypical hydrogen frameworks for clathrate hydrides, which is 1.5 times greater than the number (9) of previously reported prototypes. Remarkably, eleven ternary clathrate structures were predicted to have Tcs above 250 K at 300 GPa. Further extensive global structure-searching simulations support that Li2NaH17 and ThY2H24 are thermodynamically stable at 220 and 150 GPa, respectively, with Tcs approaching room temperature of 297 K and 303 K, which are promising for future synthesis. These results offer a platform to explore high-temperature superconductors via a great number of databases. © 2024, CC BY-NC-ND.

关键词： High temperature superconductors

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Fast and stable tight-binding framework for nonlocal kinetic energy density functional reconstruction in orbital-free density functional calculations

arXiv

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arXiv 2024年

作者： Chen, Yongshuo Ma, Cheng Cui, Boning Cui, Tian Mi, Wenhui Xu, Qiang Wang, Yanchao Ma, Yanming Key Laboratory of Material Simulation Methods & Software of Ministry of Education College of Physics Jilin University Changchun130012 China State Key Lab of Superhard Materials College of Physics Jilin University Changchun130012 China Institute of High Pressure Physics School of Physical Science and Technology Ningbo University Ningbo315211 China

Nonlocal kinetic energy density functionals (KEDFs) with density-dependent kernels are currently the most accurate functionals available for orbital-free density functional theory (OF-DFT) calculations. However, despite advances in numerical techniques and using only (semi)local density-dependent kernels, nonlocal KEDFs still present substantial computational costs in OF-DFT, limiting their application in large-scale material simulations. To address this challenge, we propose an efficient framework for reconstructing nonlocal KEDFs by incorporating the density functional tight-binding approach, in which the energy functionals are simplified through a first-order functional expansion based on the superposition of free-atom electron densities. This strategy allows the computationally expensive nonlocal kinetic energy and potential calculations to be performed only once during the electron density optimization process, significantly reducing computational overhead while maintaining high accuracy. Benchmark tests using advanced nonlocal KEDFs, such as revHC and LDAK-MGPA, on standard structures including Li, Mg, Al, Ga, Si, III-V semiconductors, as well as Mg50 and Si50 clusters, demonstrate that our method achieves orders-of-magnitude improvements in efficiency, providing a cost-effective balance between accuracy and computational speed. Additionally, the reconstructed functionals exhibit improved numerical stability for both bulk and finite systems, paving the way for developing more sophisticated KEDFs for realistic material simulations using OF-DFT. Copyright © 2024, The Authors. All rights reserved.

关键词： Kinetic energy

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