Local-Anharmonic-MD

Molecular-dynamics (MD) code in plain C implementing the local anharmonicity approximation: each atom moves in an anharmonically corrected local potential instead of the full harmonic force-constant model, capturing the dominant anharmonic contributions to vibrational free energies at a fraction of the cost of ab-initio MD. Related publication: Glensk et al., Phys. Rev. Lett. 114, 195901 (2015).

Build

cc -O2 -o md_long md_long_tox.c -lm

No dependencies beyond a C compiler and libm.

Usage

./md_long T dt L l r v w h f u wrp

Arg	Meaning
T	temperature in K (sets energy per degree of freedom)
dt	time step in ps
L	number of time steps to simulate
l	write positions every l steps
r	read a POSITIONs trajectory file (1) instead of simulating
v	verbosity: 0 silent, 1 verbose, 2 very verbose
w	write MD-analysis output files (1)
h	read a hessematrix_sphinx Hesse-matrix file (1)
f	read forces (1)
u	read u_OUTCAR displacements (1)
wrp	write positions relative to equilibrium (1)

Running with no arguments prints this usage summary.

Inputs and outputs

• Inputs (depending on flags): POSITIONs trajectory, hessematrix_sphinx (Hesse matrix, SPHInX format), u_OUTCAR displacements.
• Outputs: out_info.txt (run log), cell, out_EqCoords_direct (equilibrium coordinates), out_positions.dat, and out_analyze_positions_distances_*.dat (displacement statistics vs. equilibrium, nearest-neighbour projections).

Citation

If you use this code in your research, please cite:

A. Glensk, B. Grabowski, T. Hickel, J. Neugebauer, Phys. Rev. Lett. 114, 195901 (2015). doi:10.1103/PhysRevLett.114.195901

License

MIT