Synopsis

This analyzer a hierarchical block-averaging algorithm to calculate the shear-stress autocorrelation function for a fluid, and reports the corresponding shear relaxation modulus.

See also: DdMd::StressAutoCorrelation

Parameters

The parameter file format is:

StressAutoCorrelation{
  interval             int
  outputFileName       string
  bufferCapacity       int
}

in which

interval	number of steps between data samples
outputFileName	name of output file
bufferCapacity	Number of samples in the data history array

Output

After the end of the simulation, if the OUTPUT_ANALYZERS command is invoked:

A copy of the parameter file block associated with this analyzer is echoed to file {outputFileName}.prm.
The final stress relaxation function is output to a file {outputFileName}.dat.

Each line of the *.dat file containing the stress relaxation function has the format:

i F(t_{i})

in which i is an integer time separation index, measured in terms of the number of samples, and

$F(t) = k_{B}TG(t)$

where $G(t)$ is the shear stress relaxtion modulus evaluated at a time separation $t_{i}$ . The time separation $t_{i}$ corresponding to the integer time index i is

$t_i \equiv i*interval*\Delta t$

where interval is the number of time steps between stress measurements, as given in the parameter file, and $\Delta t$ is the molecular dynamics time step.