AIMD Tutorial 2018 08 31 INCAR For AIMD

AIMD Tutorial 2018 -08 -31

INCAR (For AIMD) • NSW = 5000 ! # of steps • IBRION = 0 ! how the ions are updated and moved; Verlet algorithm for AIMD ! Others for relaxations into a local energy minimum ! SMASS allows additional control • ISIF = 2 ! Fixed cell (volume) parameter & ionic relaxation • SMASS = 0 ! canonical ensemble is simulated using the algorithm of Nosé • POTIM = 0. 5 [fs] ! Time-step • TEBEG = 300 [K] ! Room Temp. ; control the temperature during an ab-initio mulecular dynamics ! No initial velocities on the POSCAR file the velocities set randomly (Maxwell-Boltzmann distribution) -------------------------------------------------------------------------- • # PREC = High ! Precision; set ENCUT if no values is given for ENCUT • ENCUT = 600 [e. V] ! Cut-off energy for plane wave basis set in e. V • ISPIN = 2 ! spin polarized calculations • NELM = 999 ! maximum number of electronic SC (self-consistency) steps • IDIPOL = 3 ! dipole moment

POSCAR 1: Comment line 2: Lattice constant 3 -5: lattice vector 6 -7: atomic species and number of atoms 8: Selective dynamics (optional) 9: Cartesian or in direct (fractional) Coordinates of atoms Switch on or not ‘Selective dynamics’ (F=fix, T=move)

POTCAR (C) PAW_PBE C 08 Apr 2002 4. 000000000 parameters from PSCTR are: VRHFIN =C: s 2 p 2 LEXCH = PE ! Exchange-correlation type (PBE) EATOM = 147. 1560 e. V, 10. 8157 Ry TITEL = PAW_PBE C 08 Apr 2002 LULTRA = F use ultrasoft PP or not IUNSCR = 0 unscreen: 0 -lin 1 -nonlin 2 -no RPACOR =. 000 partial core radius POMASS = 12. 011; ZVAL = 4. 000 mass and valenz RCORE = 1. 500 outmost cutoff radius RWIGS = 1. 630; RWIGS =. 863 wigner-seitz radius (au A) ENMAX = 400. 000; ENMIN = 300. 000 e. V ICORE = 2 local potential LCOR = T correct aug charges LPAW = T paw PP EAUG = 644. 873 DEXC =. 000 RMAX = 2. 266 core radius for proj-oper RAUG = 1. 300 factor for augmentation sphere RDEP = 1. 501 radius for radial grids RDEPT = 1. 300 core radius for aug-charge QCUT = -5. 516; QGAM = 11. 032 optimization parameters Description (? ) l E TYP RCUT 0. 000 23 1. 200 1. 000 23 1. 500 1 2. 500 23 1. 500 2. 000 7 1. 500 Error from kinetic energy argument (e. V) NDATA = 100 STEP = 20. 000 1. 050 • Differences of POTCAR-type https: //cms. mpi. univie. ac. at/vasp/Recommended_PAW_potentials_DFT_calc ulations_using_vasp_5_2. html 1. 2. 3. 4. 5. _h: potential is harder than the standard (greater energy cutoff) _s: potential is softer than the standard _pv and _sv: p and s semi-core states are treated as valence states (i. e. for V_pv the 3 p states are treated as valence states, and for V_sv the 3 s and 3 p states are treated as valence states) _d: d semi core states as valence states Nothing: standard version

POTCAR • • • PSCTR: The PSCTR file controls the pseudopotential generation program and the calculation of the US pseudopotentials VRHFIN: get the valence electron configuration LEXCH: hybrid functional EATOM: the "energy of the pseudo-atom", which the pseudopotential (PP) was generated. RPACOR: partial core radius Example RCORE: outmost cutoff radius POMASS: atomic mass [a. u. ] ZVAL: valence for each atomic species ICORE: local potential LCOR: correct AUG charges RMAX: maximum radius for non-local projection operators QCUT: low q-value for optimization

KPOINT K-points 0 Monkhorst 221 000 ! number of k-points = 0; automatic generation scheme ! Monkhorst-pack ! k-point grids along reciprocal vectors ! optional; shift of the mesh • Reciprocal lattice = 역벡터를 적용해 얻어지는 가상의 격자 • Periodicity (Bloch theorem apply) Brillouin zone of reciprocal space • K-point = sampling points in 1 st BZ • determines how many k-points are used to sample the Brillouin zone • when more k-points are used, only the interaction between the atoms (which should be zero) is described more accurately • 3 rd line: G/g for generating meshes at the Gamma point; M/m selects Monkhorst-Pack scheme. r. l. vector ai, bi, ci P. E. Blöchl, ``Projector augmented-wave method'', Phys. Rev. B 50, 17953 (1994). G. Kresse, and J. Joubert, ``From ultrasoft pseudopotentials to the projector augmented wave method'', Phys. Rev. B 59, 1758 (1999).

https: //cms. mpi. univie. ac. at/wiki/index. php/KPOINTS KPOINT http: //cms. mpi. univie. ac. at/wiki/index. php/KPOINTS#Automati c_k-mesh_generation • Automatically generated k-point: in output file IBZKPT Cartesian (fcc-lattice) • three possible input formats (simple, normal, expert) 0. 25 0 0 • Here one can provide directly the generating basis vectors for the kpoint mesh (in cartesian or reciprocal coordinates). The input file has the following format: 0 0. 25 0 Automatic generation 0 Cartesian 0. 25 0. 00 0. 25 0 0 0. 25 0. 5 is equivalent to Monkhorst-pack 444 000

OSZICAR and stdout. txt file

OUTCAR – informations individual parts are separated by lines -----------------------------�� • first part: reading INCAR, POTCAR, POSCAR • nearest neighbor distances and analysis of symmetry • information on what was parsed from INCAR • verbose job information • information on lattice, k-points and positions • information on the basis set (number of plane waves) • non local pseudopotential information • information for each electronic step (one line in OSZICAR)

OUTCAR – writing • contributions to electronic energy at each electronic iteration • convergence information: each electronic step • Eigenvalues: each ionic step • DOS + charge density: each ionic step • total energy and electronic contributions: each ionic step • Stress: each ionic step • basis vectors: each ionic step • Forces: each ionic step

OUTCAR - example

OUTCAR – example

References • K-points : Chadi, Cohen, PRB 8 (1973) 5747 • 첨부파일 6_k-points. pdf : “Sampling the Brillouin-zone”, Andreas EICHLER • Monk. Horst-Pack : Hendrik J. Monkhorst and James D. Pack, Phys. Rev. B 1976, 13, 5188 • “Ab-initio molecular dynamics: theory and implementation”, Dominik Marx and Jurg Hutter