VASP Force Correction Patch

Force correction patch for VASP 5.4.4 and 6.4.1

Installation

in the src folder,

patch -i "path_to_patch_file"/force_correction.patch

How to use

There are 6 new INCAR tags from the patch.

FORCES_X : Individual forces of ions in the x direction, in the order that appears in POSCAR. Corresponds to Born effective charge tensor component $Z^*_{\alpha x}$ in constrained-forces calculation, where the electric field direction is $\alpha$. Default is 0 for all ions.

FORCES_Y : Individual forces of ions in the y direction, in the order that appears in POSCAR. Corresponds to Born effective charge tensor component $Z^*_{\alpha y}$ in constrained-forces calculation, where the electric field direction is $\alpha$. Default is 0 for all ions.

FORCES_Z : Individual forces of ions in the z direction, in the order that appears in POSCAR. Corresponds to Born effective charge tensor component $Z^*_{\alpha z}$ in constrained-forces calculation, where the electric field direction is $\alpha$. Default is 0 for all ions.

SCALING : Sets the scaling parameter of forces. Corresponds to $-\mathcal{E}$ (electric field, V/Å) in constrained-forces calculation. Default is 0.

LFIX_XY : Does not relax lattice vector a and b if set to TRUE. (perpendicular z) Default is FALSE.

LFIX_Z : Does not relax lattice vector c if set to TRUE. (perpendicular z) Default is FALSE.

There are 2 new INCAR tags for VASP 6 patch, LFIX_XY_COL and LFIX_Z_COL. They fix Cartesian components of the lattice vector, instead of the vector themselves.

Both IBRION=1 and IBRION=2 works, but if you're trying to converge to a saddle point, only IBRION=1 works.

⚠️ Symmetry is your enemy! ⚠️

If you're trying to polarize your structure starting from non-polar one, you have to either set ISYM to 0 or alter your POSCAR so that it is the same space group of the polarized structure. In general, It is recommended to set ISYM to 0 to avoid internal symmetrization of k-points, unless you have a good idea of symmetry in your polarized system.

Tutorial

https://seongjoojung.github.io/posts/force-correction-tutorial/

Reference

Fu, H., & Bellaiche, L. (2003) Phys. Rev. lett. 91(5), 057601.

Jung at el. (2023) Nat. Comm. 14, 7795

Sai, Rabe & Vanderbilt (2002) Phys. Rev. B 66, 104108

Disclaimer

VASP is commercial package requiring a valid liscence for use.