Magnesium and its compounds are recognized as favorable materials for structural uses,primarily due to their lightweight nature and remarkable specific strength.This research employed first-principles methodologies to...Magnesium and its compounds are recognized as favorable materials for structural uses,primarily due to their lightweight nature and remarkable specific strength.This research employed first-principles methodologies to investigate how pressure affects the crystal structure along with the elastic and thermodynamic characteristics of MgXY_(2)(X=Zn,Cd,and Y=Ag,Au,Cu)compounds.All analyses were implemented via the Perdew-Burke-Ernzerhof variant of the Generalized Gradient Approximation alongside a plane-wave ultrasoft pseudopotential approach.The findings on the elastic constants indicated that these MgXY_(2)compounds have maintained their stability at pressures up to 500 kBar.These constants informed detailed assessments of properties like elastic modulus,Poisson’s ratio,Vickers hardness,and material anisotropy.The Quantum Espresso software was utilized to calculate melting points,Debye temperature,and minimum thermal conductivity values.A temperature range spanning from 0 to 800 K allowed for an evaluation of vibrational energy,free energy,entropy,and specific heat capacity metrics.The anticipated physical attributes suggest significant potential for these magnesium compounds in biomedical fields.展开更多
We investigated the electronic heat capacity, thermal conductivity, and resistivity of UN using Quantum Espresso and EPW code. GGA, PBEsol functional was used. The calculated electronic heat coefficient was found to b...We investigated the electronic heat capacity, thermal conductivity, and resistivity of UN using Quantum Espresso and EPW code. GGA, PBEsol functional was used. The calculated electronic heat coefficient was found to be significantly reduced (0.0176 J<span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>mol<sup><span style="white-space:nowrap;">-</span>1</sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>K<sup><span style="white-space:nowrap;">-</span>2</sup> versus 0.0006 J<span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>mol<sup><span style="white-space:nowrap;">-</span>1</sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>K<sup><span style="white-space:nowrap;">-</span>2</sup>) when the non-local hybrid functional (B3LYP) was used. Furthermore, we calculated electrical resistivity using a very transparent Ziman’s formula for metals with the Eliashberg transport coupling function as implemented in EPW code for non-spin-polarized calculations. The number of mobile electrons in UN, as a function of temperature, was derived from the ratio of the calculated resistivity and available experimental data. The electronic thermal conductivity was evaluated from the calculated electronic resistivity via Wiedemann-Franz law with the number of mobility electrons (<em>n<sub>av</sub></em>) incorporated (averaged over the temperature range 300 K - 1000 K). Both the electronic thermal conductivity and resistivity, as calculated using newly evaluated <em>n<sub>av</sub></em>, compare well with experimental data at ~700 K, but to reproduce the observed trend as a function of temperature, the number of mobile electrons must decrease with the temperature as evaluated.展开更多
In this study,we introduce a novel implementation of density functional theory integrated with single-site dynamical mean-field theory to investigate the complex properties of strongly correlated materials.This ab ini...In this study,we introduce a novel implementation of density functional theory integrated with single-site dynamical mean-field theory to investigate the complex properties of strongly correlated materials.This ab initio many-body computational toolkit,termed Zen,utilizes the VASP and Quantum ESPRESSO codes to perform first-principles calculations and generate band structures for realistic materials.The challenges associated with correlated electron systems are addressed through two distinct yet complementary quantum impurity solvers:the natural orbitals renormalization group solver for zero temperature and the hybridization expansion continuous-time quantum Monte Carlo solver for finite temperatures.To validate the performance of this toolkit,we examine three representative cases:correlated metal SrVO_(3),unconventional superconductor La_(3)Ni_(2)O_(7),and Mott insulator MnO.The calculated results exhibit excellent agreement with previously available experimental and theoretical findings.Thus,it is suggested that the Zen toolkit is proficient in accurately describing the electronic structures of d-electron correlated materials.展开更多
Electron-phonon coupling(EPC) in bulk materials is an important effect in multifarious physical and chemical phenomena. It is the key to explaining the mechanisms for superconductivity, electronic transport, etc. The ...Electron-phonon coupling(EPC) in bulk materials is an important effect in multifarious physical and chemical phenomena. It is the key to explaining the mechanisms for superconductivity, electronic transport, etc. The EPC matrix describes the coupling of the electronic eigenstates of the studied system under the perturbation of phonons. Although the EPC matrix is closely relevant to many fundamental physicochemical properties, it remains a challenge to calculate the EPC matrix precisely due to the high computational cost. In recent years, Giustino et al. developed the EPW method on open-source ab-initio software Quantum Espresso, which uses Wannier functions(WFs) to calculate EPC matrix. However, due to the limitation of their implementation,it is not possible yet to calculate the EPC matrix under some important computational conditions, e.g., for DFT+U and HSE calculation. Given the importance of these computational conditions(e.g., for transition metal oxides), we have developed our own implementation of EPC matrix calculation based on the domestic ab-initio software PWmat. Our code allows the DFT+U and HSE correction, so we can get a more accurate EPC matrix in the related problems. In this article, we will first review the formulae and elucidate how to calculate the EPC matrix by constructing WFs. Then we will introduce our code along with its workflow on PWmat and present our test results of two classical semiconductor systems Al As and Si, showing consistency with EPW. Next, the EPC matrix of Li Co O_(2), a classical cathode material for lithium-ion batteries, is calculated using different exchange correlation(XC) functionals including LDA, PBE, DFT+U and HSE. A comparison is provided for the related EPC matrix. It shows there could be a significant difference for the EPC matrix elements due to the use of different XC functionals.Our implementation thus opens the way for fast calculation of EPC for the important class of materials, like the transition metal oxides.展开更多
基金support of the National Center for High Performance Computing(UHe M)#1012332022#。
文摘Magnesium and its compounds are recognized as favorable materials for structural uses,primarily due to their lightweight nature and remarkable specific strength.This research employed first-principles methodologies to investigate how pressure affects the crystal structure along with the elastic and thermodynamic characteristics of MgXY_(2)(X=Zn,Cd,and Y=Ag,Au,Cu)compounds.All analyses were implemented via the Perdew-Burke-Ernzerhof variant of the Generalized Gradient Approximation alongside a plane-wave ultrasoft pseudopotential approach.The findings on the elastic constants indicated that these MgXY_(2)compounds have maintained their stability at pressures up to 500 kBar.These constants informed detailed assessments of properties like elastic modulus,Poisson’s ratio,Vickers hardness,and material anisotropy.The Quantum Espresso software was utilized to calculate melting points,Debye temperature,and minimum thermal conductivity values.A temperature range spanning from 0 to 800 K allowed for an evaluation of vibrational energy,free energy,entropy,and specific heat capacity metrics.The anticipated physical attributes suggest significant potential for these magnesium compounds in biomedical fields.
文摘We investigated the electronic heat capacity, thermal conductivity, and resistivity of UN using Quantum Espresso and EPW code. GGA, PBEsol functional was used. The calculated electronic heat coefficient was found to be significantly reduced (0.0176 J<span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>mol<sup><span style="white-space:nowrap;">-</span>1</sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>K<sup><span style="white-space:nowrap;">-</span>2</sup> versus 0.0006 J<span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>mol<sup><span style="white-space:nowrap;">-</span>1</sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>K<sup><span style="white-space:nowrap;">-</span>2</sup>) when the non-local hybrid functional (B3LYP) was used. Furthermore, we calculated electrical resistivity using a very transparent Ziman’s formula for metals with the Eliashberg transport coupling function as implemented in EPW code for non-spin-polarized calculations. The number of mobile electrons in UN, as a function of temperature, was derived from the ratio of the calculated resistivity and available experimental data. The electronic thermal conductivity was evaluated from the calculated electronic resistivity via Wiedemann-Franz law with the number of mobility electrons (<em>n<sub>av</sub></em>) incorporated (averaged over the temperature range 300 K - 1000 K). Both the electronic thermal conductivity and resistivity, as calculated using newly evaluated <em>n<sub>av</sub></em>, compare well with experimental data at ~700 K, but to reproduce the observed trend as a function of temperature, the number of mobile electrons must decrease with the temperature as evaluated.
基金supported by National Natural Science Foundation of China(Grants Nos.11934020 and 12274380)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302402)+1 种基金supported by the“Qiushi Academic-Dongliang”Talent Cultivation Program of Renmin University of China(Grant No.RUC24QSDL040)Computational resources were provided by Physical Laboratory of High Performance Computing in Renmin University of China.
文摘In this study,we introduce a novel implementation of density functional theory integrated with single-site dynamical mean-field theory to investigate the complex properties of strongly correlated materials.This ab initio many-body computational toolkit,termed Zen,utilizes the VASP and Quantum ESPRESSO codes to perform first-principles calculations and generate band structures for realistic materials.The challenges associated with correlated electron systems are addressed through two distinct yet complementary quantum impurity solvers:the natural orbitals renormalization group solver for zero temperature and the hybridization expansion continuous-time quantum Monte Carlo solver for finite temperatures.To validate the performance of this toolkit,we examine three representative cases:correlated metal SrVO_(3),unconventional superconductor La_(3)Ni_(2)O_(7),and Mott insulator MnO.The calculated results exhibit excellent agreement with previously available experimental and theoretical findings.Thus,it is suggested that the Zen toolkit is proficient in accurately describing the electronic structures of d-electron correlated materials.
基金supported by the starting fund of Peking University Shenzhen Graduate SchoolFujian Science&Technology Innovation Laboratory for Energy Devices of China (Grant No. 1C-LAB)+2 种基金the Chemistry and Chemical Engineering Guangdong Laboratory (Grant No. 1922018)the Soft Science Research Project of Guangdong Province (Grant No. 2017B030301013)the Major Science and Technology Infrastructure Project of Material Genome Big-Science Facilities Platform supported by Municipal Development and Reform Commission of Shenzhen。
文摘Electron-phonon coupling(EPC) in bulk materials is an important effect in multifarious physical and chemical phenomena. It is the key to explaining the mechanisms for superconductivity, electronic transport, etc. The EPC matrix describes the coupling of the electronic eigenstates of the studied system under the perturbation of phonons. Although the EPC matrix is closely relevant to many fundamental physicochemical properties, it remains a challenge to calculate the EPC matrix precisely due to the high computational cost. In recent years, Giustino et al. developed the EPW method on open-source ab-initio software Quantum Espresso, which uses Wannier functions(WFs) to calculate EPC matrix. However, due to the limitation of their implementation,it is not possible yet to calculate the EPC matrix under some important computational conditions, e.g., for DFT+U and HSE calculation. Given the importance of these computational conditions(e.g., for transition metal oxides), we have developed our own implementation of EPC matrix calculation based on the domestic ab-initio software PWmat. Our code allows the DFT+U and HSE correction, so we can get a more accurate EPC matrix in the related problems. In this article, we will first review the formulae and elucidate how to calculate the EPC matrix by constructing WFs. Then we will introduce our code along with its workflow on PWmat and present our test results of two classical semiconductor systems Al As and Si, showing consistency with EPW. Next, the EPC matrix of Li Co O_(2), a classical cathode material for lithium-ion batteries, is calculated using different exchange correlation(XC) functionals including LDA, PBE, DFT+U and HSE. A comparison is provided for the related EPC matrix. It shows there could be a significant difference for the EPC matrix elements due to the use of different XC functionals.Our implementation thus opens the way for fast calculation of EPC for the important class of materials, like the transition metal oxides.
