compute_modify command

Syntax

compute_modify compute-ID keyword value ...

• compute-ID = ID of the compute to modify

• one or more keyword/value pairs may be listed

• keyword = extra or dynamic

  extra value = N
    N = # of extra degrees of freedom to subtract
  dynamic value = yes or no
    yes/no = do or do not recompute the number of atoms contributing to the temperature
  

Examples

compute_modify myTemp extra 0
compute_modify newtemp dynamic yes extra 600

Description

Modify one or more parameters of a previously defined compute. Not all compute styles support all parameters.

The extra keyword refers to how many degrees-of-freedom are subtracted (typically from 3N) as a normalizing factor in a temperature computation. Only computes that compute a temperature use this option. The default is 2 or 3 for 2d or 3d systems which is a correction factor for an ensemble of velocities with zero total linear momentum. For compute temp/partial, if one or more velocity components are excluded, the value used for extra is scaled accordingly. You can use a negative number for the extra parameter if you need to add degrees-of-freedom. See the compute temp/asphere command for an example.

The dynamic keyword determines whether the number of atoms N in the compute group is re-computed each time a temperature is computed. Only compute styles that calculate a temperature use this option. By default, N is assumed to be constant. If you are adding atoms to the system (see the fix pour or fix deposit commands) or expect atoms to be lost (e.g. due to evaporation), then this option should be used to insure the temperature is correctly normalized.

Restrictions

none

Related commands

compute

Default

The option defaults are extra = 2 or 3 for 2d or 3d systems and dynamic = no.