All requests for technical support from the VASP group must be addressed to: vasp.materialphysik@univie.ac.at

LANGEVIN GAMMA

From Vaspwiki
Jump to: navigation, search

LANGEVIN_GAMMA = [Real array]
Default: LANGEVIN_GAMMA = NTYP×0 

Description: LANGEVIN_GAMMA specifies the friction coefficients (in ps-1) for atomic degrees-of-freedom when using a Langevin thermostat (in case VASP was compiled with -Dtbdyn).


When using a Langevin thermostat[1] (MDALGO=3), the friction coefficients γ for the atomic degrees-of-freedom are specified (in ps-1) using the LANGEVIN_GAMMA-tag.

One has to specify a separate friction coefficient for each of the NTYP atomic species found on the POTCAR-file.

Practical example

Consider a system consisting of 16 hydrogen and 48 silicon atoms. Suppose that eight silicon atoms are considered to be Langevin atoms and the remaining 32 Si atoms are either fixed or Newtonian atoms. The Langevin and Newtonian (or fixed) atoms should be considered as different species, i.e., the POSCAR-file should contain the line like this:

Si H Si
40 16 8

As only the final eight Si atoms are considered to be Langevin atoms, the INCAR-file should contain the following line defining the friction coefficients:

LANGEVIN_GAMMA = 0.0   0.0   10.0

i.e., for all non-Langevin atoms, γ should be set to zero.

Related Tags and Sections

LANGEVIN_GAMMA_L, MDALGO

Examples that use this tag

References

  1. M. P. Allen and D. J. Tildesley, Computer simulation of liquids, Oxford university press: New York, 1991.

Contents