relax_static calculation style
Lucas M. Hale, lucas.hale@nist.gov, Materials Science and Engineering Division, NIST.
Introduction
The relax_static calculation style uses static energy/force minimizations to relax the atomic positions and box dimensions of a system to a specified pressure.
Version notes
2018-07-09: Notebook added.
2019-07-30: Description updated and small changes due to iprPy version.
2020-05-22: Version 0.10 update - potentials now loaded from database.
2020-09-22: Setup and parameter definition streamlined.
2022-03-11: Notebook updated to reflect version 0.11.
Additional dependencies
Disclaimers
The minimization algorithm will drive the system to a local minimum, which may not be the global minimum. There is no guarantee that the resulting structure is dynamically stable, and it is possible that the relaxation of certain dimensions may be constrained to move together during the minimization preventing a full relaxation.
Method and Theory
This method uses the LAMMPS minimization plus box_relax commands to simultaneously relax both the atomic positions and the system’s box dimensions towards a local minimum. The LAMMPS documentation of the box_relax command notes that the complete minimization algorithm is not well defined which may prevent a complete relaxation during a single run. To overcome this limitation, the calculation script continuously restarts the minimization until the box dimensions from one run to the next remain within a specified tolerance.