vcrelax_vasp

This command implements the "Voronoi Cell Minimization" as part of the "Piecewise Polynomial Potential Partitioning" method introduced here.

It finds the atomic geometry of the minimum on the ab initio energy surface confined to the Voronoi tesselation of the configuration space of a structure that is mechanically unstable. It interfaces with a first-priciples code to investigate the ab initio energy surface.
In a nutshell: the method finds either a local minimum (for a mechanically stable phase) or the absolute minimum on the boundary of the Voronoi cell that defines the vicinity of an atomic configuration on the lattice (for a mechanically unstable phase).

This command does the following:
Relax the structure (in str.in or str.out) confined in the Voronoi cell generated by the lattice sites in the augmented lattice to create str_relax.out.

-> Input files:
1) lat.in : defines the augmented lattice.
2) str.in : defines the atomic structure.

See "auglat" manual page for details on structure and lattice file formats.

-> Intermediate output files:
As the optimization progresses, the current status is written to various files:
1) str_cur.out : defines the currect atomic geometry in the minimization process. Same format as in str.in.
2) force_cur.out : defines the forces acting on the current atomic positions (one 3d vector per line for each atom).

The intermediate files can be used for the -cip option to restart an aborted or misbehaving run.

-> Final output files:
1) str_relax.out : defines the relaxed atomic geometry inside the Voronoi cell.
2) force_final.out : defines the forces acting on the relaxed structure (one 3d vector per line for each atom).
3) hessian.out : defines the matrix of negative second-order partial derivatives of energy for the relaxed structure.
3) eigenvalues.out : defines the eigenvalues of the matrix in hessian.out.
3) eigenvectors.out : defines the eigenvectors of the matrix in hessian.out. Each line is an eigenvector.