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Correlation Function Tools

The following utility programs deal with correlation functions:

imd2nc.py

This program converts a .moldyn trajectory file to the netCDF format required by nMoldyn.

Usage: imd2nc.py <types> <trajectory>

   <types>:       comma-separated list of chemical symbols

   <trajectory>:  IMD trajectory file (*.nmoldyn)

Example:  imd2nc.py Al,Ni trajectory.nmoldyn

imd2nc.py is a python program, and requires a number of further packages, all of which are also required for nMoldyn. We refer to the installation instructions of nMoldyn and MMTK, on which nMoldyn is based. In particular, for each atom type a file with the coherent and incoherent scattering lengths (along with other data) must be installed in the directory $HOME/.mmtk/Database/Atoms/.

dynsf

Computes the coherent part of the dynamical structure factor from an IMD .dsf file (see option dsf).

   Usage: dynsf [options] <file.dsf>

   Compute dynamical structure factor.

   Options:  -w <width> Frequency smoothing width (FWHM)
             -i <int>   Frequency writing interval
             -c <cut>   Frequency cutoff
             -e         Frequency and width in meV (default THz)
             -s         Separate reords by two emtpy lines
             -h         This help

For each k-point series i, a separat file *.i.plot is produced, which can the be plotted with gnuplot. Each line is of the form

   frequency  k-value  dsf

Blocks with different frequencies are separated by one or two empty lines. The latter is useful if single curves at fixed k-value along the frequency direction shall be plotted. Note that a smooting value in frequency direction must be specified, which should not be too small (depending on the length of the time series), for otherwise artefacts will show up.