REWEIGHT_METAD

This is part of the bias module

Calculate the weights configurations should contribute to the histogram in a simulation in which a metadynamics bias acts upon the system.

This command allows you to use the reweighting algorithm discussed in [62] when constructing a histogram of the configurations visited during a metadynamics simulation.

Compulsory keywords

ARG	( default=*.rbias ) the biases that must be taken into account when reweighting

Options

TEMP	the system temperature. This is not required if your MD code passes this quantity to PLUMED

Examples

In the following example there is a metadynamics bias acting on the distance between atoms 1 and 2. Clearly, this bias will have an effect on the region of phase space that will be sampled when an MD simulation is run using this variable. Consequently, when the histogram as a function of the angle, \(a\), is accumulated, we use reweighting into order to discount the effect of the bias from our final histogram. We do not use REWEIGHT_BIAS here, however, as the bias changes with time. We thus use the reweighting algorithm for metadynamics instead. Notice also that we have to specify how often we would like to calculate the c(t) reweighting factor and the grid over which we calculate c(t) in the input to the METAD command.

a: ANGLE ATOMS=1,2,3
x: DISTANCE ATOMS=1,2
METAD ARG=x PACE=100 SIGMA=0.1 HEIGHT=1.5 BIASFACTOR=5 GRID_MIN=0 GRID_MAX=10 GRID_BIN=100 REWEIGHTING_NGRID=100 REWEIGHTING_NHILLS=50

bias: REWEIGHT_METAD TEMP=300

HISTOGRAM ...
  ARG=a
  GRID_MIN=0.0
  GRID_MAX=pi
  GRID_BIN=100
  BANDWIDTH=0.1
  LOGWEIGHTS=bias
  LABEL=hB
... HISTOGRAM

DUMPGRID GRID=hB FILE=histoB STRIDE=1 FMT=%8.4f