WHAM_WEIGHTS

This is part of the analysis module

Calculate and output weights for configurations using the weighted histogram analysis method.

This shortcut action allows you to calculate and output weights computed using the weighted histogram analysis technique. For more detail on how this technique works see REWEIGHT_WHAM

Compulsory keywords

BIAS	( default=*.bias ) the value of the biases to use when performing WHAM
TEMP	the temperature at which the simulation was run
STRIDE	( default=1 ) the frequency with which the bias should be stored to perform WHAM
FILE	the file on which to output the WHAM weights

Options

FMT	the format to use for the real numbers in the output file

Examples

The following input can be used to analyze the output from a series of umbrella sampling calculations. The trajectory from each of the simulations run with the different biases should be concatenated into a single trajectory before running the following analysis script on the concatenated trajectory using PLUMED driver. The umbrella sampling simulations that will be analyzed using the script below applied a harmonic restraint that restrained the torsional angle involving atoms 5, 7, 9 and 15 to particular values. The script below calculates the reweighting weights for each of the trajectories and then applies the binless WHAM algorithm to determine a weight for each configuration in the concatenated trajectory.

phi: TORSION ATOMS=5,7,9,15
rp: RESTRAINT ARG=phi KAPPA=50.0 ...
  AT=@replicas:{
        -3.00000000000000000000
        -2.22580645161290322584
        -1.45161290322580645168
        -.67741935483870967752
        .09677419354838709664
        .87096774193548387080
        1.64516129032258064496
        2.41935483870967741912
     }
...

WHAM_WEIGHTS BIAS=rp.bias TEMP=300 FILE=wham-weights

The script above must be run with multiple replicas using the following command:

mpirun -np 6 plumed driver --mf_xtc alltraj.xtc --multi 6