We report structural and electronic properties of Na_(2)Ni_(3)S_(4),a quasi-two-dimensional compound composed of alternating layers of[Ni_(3)S_(4)]^(2-)and Na^(+).The compound features a remarkable Ni-based kagome lat...We report structural and electronic properties of Na_(2)Ni_(3)S_(4),a quasi-two-dimensional compound composed of alternating layers of[Ni_(3)S_(4)]^(2-)and Na^(+).The compound features a remarkable Ni-based kagome lattice with a square planar configuration of four surrounding S atoms for each Ni atom.Magnetization and electrical measurements reveal a weak paramagnetic insulator with a gap of about 0.5 eV.Our band structure calculation highlights a set of topological flat bands of the kagome lattice derived from the rotated dxz-orbital with C_(3)+T symmetry in the presence of crystal-field splitting.展开更多
The k·p method is significant in condensed matter physics for the compact and analytical Hamiltonian.In the presence of magnetic field,it is described by the effective Zeeman's coupling Hamiltonian with Land&...The k·p method is significant in condensed matter physics for the compact and analytical Hamiltonian.In the presence of magnetic field,it is described by the effective Zeeman's coupling Hamiltonian with Landég-factors.Here,we develop an open-source package VASP2KP(including two parts:vasp2mat and mat2kp)to compute k·p parameters and Landég-factors directly from the wavefunctions provided by the density functional theory(DFT)as implemented in Vienna ab initio Simulation Package(VASP).First,we develop a VASP patch vasp2mat to compute matrix representations of the generalized momentum operatorπ=p+1/2mc^(2)[s×■V(r)],spin operator s,time reversal operatorT,and crystalline symmetry operatorsR on the DFT wavefunctions.Second,we develop a python code mat2kp to obtain the unitary transformation U that rotates the degenerate DFT basis towards the standard basis,and then automatically compute the k·p parameters and g-factors.The theory and the methodology behind VASP2KP are described in detail.The matrix elements of the operators are derived comprehensively and computed correctly within the projector augmented wave method.We apply this package to some materials,e.g.,Bi2Se3,Na3Bi,Te,InAs and 1H-TMD monolayers.The obtained effective model's dispersions are in good agreement with the DFT data around the specific wave vector,and the g-factors are consistent with experimental data.The VASP2KP package is available at https://github.com/zjwang11/VASP2KP.展开更多
HEDS电动机跟一般同步电动机相比性能更加优良,跟一般异步电动机作比对,HEDS电动机拥有较小的体积,较轻的机身重量,较高的工作效率并且节能性能更加优越。为了进一步提高HEDS电动机输出转矩与输出功率,仍需要对电动机主要结构参数进行...HEDS电动机跟一般同步电动机相比性能更加优良,跟一般异步电动机作比对,HEDS电动机拥有较小的体积,较轻的机身重量,较高的工作效率并且节能性能更加优越。为了进一步提高HEDS电动机输出转矩与输出功率,仍需要对电动机主要结构参数进行最优化设计。电动机的实际运行工况可以通过Ansys软件进行仿真,使电动机模型的分析更加容易。通过利用Ansys仅对HEDS电动机气隙之间的长度、定转子齿相对长度及转子极弧三个主要结构参数对电动机转矩特性的作用进行模拟,通过改变参数的大小观察电动机的转矩特性,实现了对750 W HEDS电动机结构参数的优化,并通过对样机的测试验证了理论分析的合理性。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12141002 and 12225401)the National Key Research and Development Program of China(Grant No.2021YFA1401902)+1 种基金the CAS Interdisciplinary Innovation Teamthe Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)。
文摘We report structural and electronic properties of Na_(2)Ni_(3)S_(4),a quasi-two-dimensional compound composed of alternating layers of[Ni_(3)S_(4)]^(2-)and Na^(+).The compound features a remarkable Ni-based kagome lattice with a square planar configuration of four surrounding S atoms for each Ni atom.Magnetization and electrical measurements reveal a weak paramagnetic insulator with a gap of about 0.5 eV.Our band structure calculation highlights a set of topological flat bands of the kagome lattice derived from the rotated dxz-orbital with C_(3)+T symmetry in the presence of crystal-field splitting.
基金supported by the National Key R&D Program of Chain(Grant No.2022YFA1403800)the National Natural Science Foundation of China(Grant Nos.11974395,12188101,11925408,12274436,and 11921004)+5 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000)the Center for Materials Genomesupported by the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302403)the National Natural Science Foundation of China(Grant No.12274005)the National Key Research and Development Program of China(Grant No.2021YFA1401900)supported by the Informatization Plan of the Chinese Academy of Sciences(Grant No.CASWX2021SF0102)。
文摘The k·p method is significant in condensed matter physics for the compact and analytical Hamiltonian.In the presence of magnetic field,it is described by the effective Zeeman's coupling Hamiltonian with Landég-factors.Here,we develop an open-source package VASP2KP(including two parts:vasp2mat and mat2kp)to compute k·p parameters and Landég-factors directly from the wavefunctions provided by the density functional theory(DFT)as implemented in Vienna ab initio Simulation Package(VASP).First,we develop a VASP patch vasp2mat to compute matrix representations of the generalized momentum operatorπ=p+1/2mc^(2)[s×■V(r)],spin operator s,time reversal operatorT,and crystalline symmetry operatorsR on the DFT wavefunctions.Second,we develop a python code mat2kp to obtain the unitary transformation U that rotates the degenerate DFT basis towards the standard basis,and then automatically compute the k·p parameters and g-factors.The theory and the methodology behind VASP2KP are described in detail.The matrix elements of the operators are derived comprehensively and computed correctly within the projector augmented wave method.We apply this package to some materials,e.g.,Bi2Se3,Na3Bi,Te,InAs and 1H-TMD monolayers.The obtained effective model's dispersions are in good agreement with the DFT data around the specific wave vector,and the g-factors are consistent with experimental data.The VASP2KP package is available at https://github.com/zjwang11/VASP2KP.
文摘HEDS电动机跟一般同步电动机相比性能更加优良,跟一般异步电动机作比对,HEDS电动机拥有较小的体积,较轻的机身重量,较高的工作效率并且节能性能更加优越。为了进一步提高HEDS电动机输出转矩与输出功率,仍需要对电动机主要结构参数进行最优化设计。电动机的实际运行工况可以通过Ansys软件进行仿真,使电动机模型的分析更加容易。通过利用Ansys仅对HEDS电动机气隙之间的长度、定转子齿相对长度及转子极弧三个主要结构参数对电动机转矩特性的作用进行模拟,通过改变参数的大小观察电动机的转矩特性,实现了对750 W HEDS电动机结构参数的优化,并通过对样机的测试验证了理论分析的合理性。
