openmaterials.ai / codes / VASP

VASP: plane-wave DFT with the projector augmented-wave method

A plane-wave code built on RMM-DIIS iterative diagonalization and Pulay density mixing, with a PAW formulation that reproduces all-electron bond lengths to within 0.5 percent.

What it is and how it works

PAW from ultrasoft pseudopotentials

The ultrasoft total energy follows from linearizing two terms of a modified PAW functional. With its Hamiltonian, forces and stress tensor, PAW fits into plane-wave codes that support ultrasoft potentials (Kresse 1999).

Self-consistency cycle

RMM-DIIS diagonalization alternates with Pulay mixing of the charge density. The iteration count to a given precision is almost independent of system size (Kresse 1996).

Scaling

Time per iteration grows as N squared in the atom count up to 1000 electrons. A 256 MB workstation handled 100 transition metal or 200 simple element atoms (Kresse 1996).

Magnetic metals

PAW energies of Fe, Co and Ni atoms are within 10 meV of all-electron values. Standard ultrasoft potentials overestimate the bcc Fe magnetic energy by 120 meV in GGA.

Inputs and outputs on the map

Structures enter as POSCAR and leave as CONTCAR. Energies, forces, stresses, Born charges, dielectric and elastic tensors come from OUTCAR and vasprun.xml.

What people do with it

  • 0.5%bond length error, PAW vs all-electron, 400 eVKresse 1999
  • 11 GPaPAW FM bcc to NM hcp transition pressure, FeKresse 1999
  • 1000electrons up to which N squared scaling holdsKresse 1996

Electron heat capacity of hot metals

PAW GGA densities of states on a 31x31x31 mesh for Al, Cu, Ag, Au, Ni, Pt, W and Ti. Coupling and heat capacity deviate up to an order of magnitude from the linear and constant models. Lin 2008

Anharmonicity of SnSe

PAW PBE phonons in a 112-atom supercell give average Gruneisen parameters of 4.1, 2.1 and 2.3 along a, b and c. The DFT minimum lattice conductivity along a at 770 K is 0.256 W/m/K. Zhao 2014

How it is used

  1. Prepare the inputs

    POSCAR for the cell and positions, POTCAR with PAW datasets, KPOINTS and INCAR.

  2. Converge the ground state

    Davidson or RMM-DIIS steps with Pulay mixing until the energy and forces settle.

  3. Relax or perturb

    Ionic relaxation to CONTCAR, or finite displacements and fields for phonons and tensors.

  4. Parse the results

    pymatgen and atomate2 read OUTCAR and vasprun.xml into the map quantities.