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在线讨论:使用vasp,exciting计算材料的磁性问题
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受csfn兄的号召，引用wuchenwf兄弟的话“我个人水平有限，所以在此抛砖引玉。” 本人主要关注稀磁半导体的磁性问题，常用的软件主要有vasp, exiting(FLAPW), abinit, pwscf也会使用一些。希望在此和各位朋友共同探讨遇到的问题。 在此先介绍几个优秀的开源软件，大家熟悉的abinit, pwscf就不说了。 1 exciting (http://exciting.sourceforge.net/)Features General • FP-LAPW basis with local-orbitals • APW radial derivative matching to arbitrary orders at muffin-tin surface (super-LAPW, etc.) • Arbitrary number of local-orbitals allowed (all core states can be made valence for example) • Every element in the periodic table available • Total energies resolved into components • LSDA and GGA functionals available • Core states treated with the radial Dirac equation • Simple to use: just one input file required with all input parameters optional • Multiple tasks can be run consecutively Structure and symmetry • Determination of lattice and crystal symmetry groups from input lattice and atomic coordinates • Determination of atomic coordinates from space group data (with the Spacegroup utility) • XCrysDen and V_Sim file output • Automatic reduction from conventional to primitive unit cell • Automatic determination of muffin-tin radii • Full symmetrisation of density and magnetisation and their conjugate fields • Automatic determination and reduction of the k-point set Magnetism • Spin polarised calculations performed in the most general way: only (n(r); m(r)) and (vs(r); Bs(r)) are referred to in the code • Spin symmetry broken by infinitesimal external fields • Spin-orbit coupling (SOC) included in second-variational scheme • Non-collinear magnetism (NCM) with arbitrary on-site magnetic fields • Fixed spin-moment calculations (with SOC and NCM) • Spin-spirals for any q-vector (conical spirals are still experimental) Plotting • Band structure plotting with angular momentum character • Total and partial density of states with irreducible representation projection • Charge density plotting (1/2/3D) • Plotting of exchange-correlation and Coulomb potentials (1/2/3D) • Electron localisation function (ELF) plotting (1/2/3D) • Fermi surface plotting (3D) • Magnetisation plots (2/3D) • Plotting of exchange-correlation magnetic field, Bxc (2/3D) • Plotting of ∇⋅Bxc (1/2/3D) • Wavefunction plotting (1/2/3D) • Electric field (E=-&nabla V) plotting (1/2/3D) • Simple scanning tunnelling microscopy (STM) imaging based on the local density of states (LDOS) (experimental) Forces and phonons • Forces - including incomplete basis set (IBS) and core corrections • Forces work with spin-orbit coupling, non-collinear magnetism and LDA+U • Structural optimisation • Phonons for arbitrary q-vectors (experimental) • Phonon dispersion and density of states • Thermodynamic quantities calculated from the phonon DOS: free energy, entropy, heat capacity • Phonon calculations can be distributed across networked computers • Electron-phonon coupling matrices • Phonon linewidths • Eliashberg function, α2F(ω) • Electron-phonon coupling constant, λ • McMillan-Allen-Dynes critical temperature, Tc Advanced • Exact exchange (EXX) optimised effective potential (OEP) method (with SOC and NCM) (experimental) • EXX energies (with SOC and NCM) (experimental) • Hartree-Fock for solids (with SOC and NCM) (experimental) • LDA+U: fully localised limit (FLL), around mean field (AFM) and interpolation between the two; works with SOC, NCM and spin-spirals (experimental) • Reduced density matrix functional theory (RDMFT) for solids (experimental) Miscellaneous • Mössbauer hyperfine parameters: isomer shift, EFG and hyperfine contact fields (experimental) • First-order optical response • Kerr angle and Magneto-Optic Kerr Effect (MOKE) output (experimental) • Generalised DFT correction of L. Fritsche and Y. M. Gu, Phys. Rev. B 48, 4250 (1993) (experimental) • Energy loss near edge structure (ELNES) • L, S, and J expectation values • Effective mass tensor for any state • Equation of state fitting (with the EOS utility) Programming • Clean, simple code structure - ideal for development • OpenMP parallelisation over k-vectors • Strict Fortran 90 compliance • Only one language used • Free-form style input file • Full LaTeX documentation included with every subroutine 2 OpenMX (http://www.openmx-square.org/whatisopenmx.html) OpenMX (Open source package for Material eXplorer) is a program package for nano-scale material simulations based on density functional theories (DFT) [1], norm-conserving pseudopotentials [2,20,21], and pseudo-atomic localized basis functions [23]. Since the code is designed for the realization of large-scale ab initio calculations on parallel computers, it is anticipated that OpenMX can be a useful and powerful tool for nano-scale material sciences in a wide variety of systems such as biomaterials, carbon nanotubes, magnetic materials, and nanoscale conductors. The distribution of the program package and the source codes follow the practice of the GNU General Public License (GPL) [39], and they are downloadable from http://www.openmx-square.org/ Features and capabilities of OpenMX Ver. 3.2 are as follows: Total energy and forces by cluster, band, and O() methods Local density approximation (LDA, LSDA) [2,3,4] and generalized gradient approximation (GGA) [5] to the exchange-correlation potential Norm-conserving pseudopotentials [2,20,21] Variationally optimized pseudo-atomic basis functions [23] Fully and scalar relativistic treatment within pseudopotential scheme [10,19,13] Non-collinear DFT [6,7,8,9] Constraint DFT for non-collinear spin and orbital orientation [11] Collinear LDA+U and non-collinear LDA+U methods [16] Macroscopic polarization by Berry's phase [12] Electric transport calculation by a non-equilibrium Green's function method Divide-conquer (DC) method [28], generalized DC method, and Krylov subspace method for O() eigenvalue solver Simple, RMM-DIIS [31], GR-Pulay [30], Kerker [32], and RMM-DIIS with Kerker's metric [31] charge mixing schemes Exchange coupling parameter [14,15] Optical conductivity Charge doping Uniform electric field Full and constrained geometry optimization NVE ensemble molecular dynamics NVT ensemble molecular dynamics by a velocity scaling [17] and the Nose-Hoover methods [18] Mulliken, Voronoi, and ESP fitting analysis of charge and spin densities Analysis of wave functions and electron (spin) densities Dispersion analysis by the band calculation Density of states (DOS) and projected DOS Flexible data format for the input Completely dynamic memory allocation Parallel execution by Message Passing Interface (MPI) Useful user interface for developers Evaluation of two-center integrals using Fourier transformation [27] Evaluation of three-center integrals by a projector expansion method [24] Solution of Poisson's equation using FFT [26] Considerable functionalities are available for calculations of physical properties such as magnetic, dielectric, electric transport properties as listed above. Not only conventional diagonalization schemes are provided for clusters, molecules, slab, and solids, but also linear scaling methods are supported as the eigenvalue solver. Three calculation parts in OpenMX are mainly time-consuming: Evaluation of Hamiltonian matrix elements Solution of Poisson's equation Diagonalization of the generalized secular equation For the first and second parts, the computational time always scales as O() and O() for any eigenvalue solver, where is the number of atoms, basis functions, or grid points. When the conventional diagonalization scheme (cluster and band methods) is used, the computational time for the third part scales as O(). On the other hand, the O() methods can solve the eigenvalue problem in O() operation in exchange for accuracy. For large scale calculations parallel execution by MPI is supported for parallel machines with distributed memories. Also all work arrays in the program codes are dynamically allocated with the minimum memory size required to an input file. The execution environment is unix and linux. For the execution of OpenMX, you are required to have pseudo-atomic basis orbitals and pseudopotentials. These input data can be calculated using ADPACK which is a program package for atomic density functional calculations. Conveniently, the data for several elements and ADPACK are available from a web site (http://www.openmx-square.org/). We are continuously working toward development. Motivated contributors who want to develop the open source codes are welcome. If so, the contact information is available in the above website. [ Last edited by woshilsh on 2009-6-13 at 22:27 ] |
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csfn
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2楼2008-12-04 13:28:29
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1，OSZICAR中得到的磁矩是OUTCAR中最后一步得到的总磁矩是相等的。总磁矩和各原子的磁矩(RMT球内的磁矩)之和之差就是间隙区的磁矩。因为有间隙区存在,不一致是正常的。 2，如果算磁性，全电子的结果更精确，我的一些计算结果显示磁性原子对在最近邻的位置时，PAW与FPLAW给出的能量差不一致，在长程时符合的很好。虽然并没有改变定性结论。感觉PAW似乎不能很好地描述较强耦合。我试图在找出原因，主要使用exciting和vasp做比较。计算磁性推荐使用FP-LAPW, FP-LMTO, FPLO很吸引人(不过是商业的)，后者是O(N)算法。 3，使用vasp计算磁性，注意不同的初始磁矩是否收敛为同一个磁矩。倒没有特别要注意的地方，个人认为。 归根结底，需要一个优秀的交换关联形式出现。 |
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