NVT ensemble: Difference between revisions

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  This page describes how to sample the NVT ensemble from a [[Molecular dynamics calculations|molecular dynamics]] run.  
  This page describes how to sample the NVT ensemble from a [[Molecular dynamics calculations|molecular dynamics]] run.  
   
   
  == Instructions for setting up a NVT ensemble ==
  ''' Instructions for setting up a NVT ensemble '''
  There are 4 choices of thermostats which can either be stochastic or deterministic to simulate the NVT ensemble.  
  There are 4 choices of thermostats which can either be stochastic or deterministic to simulate the NVT ensemble.  
  The stochastic [[Andersen thermostat]] or [[Langevin thermostat]],
  The stochastic [[Andersen thermostat]] or [[Langevin thermostat]],
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  The user is not allowed to set ISF>2 because then the volume of the simulation would be allowed to change
  The user is not allowed to set ISF>2 because then the volume of the simulation would be allowed to change
  and the simulation would not result in a NVT ensemble. Setting ISIF=0 will speed up the calculation because the stress
  and the simulation would not result in a NVT ensemble. Setting ISIF=0 will speed up the calculation because the stress
  tensor is not computed.
  tensor is not computed. The tag {{TAG|IBRION}} has to be set to zero.

Revision as of 13:01, 19 July 2022

Category: NVT ensemble

== NVT ensemble ==
The NVT ensemble is a statistical ensemble that is used to study material properties under the conditions of a 
constant particle number N, constant volume V and a temperature fluctuating around an equilibrium value T.
This page describes how to sample the NVT ensemble from a molecular dynamics run. 

 Instructions for setting up a NVT ensemble 
There are 4 choices of thermostats which can either be stochastic or deterministic to simulate the NVT ensemble. 
The stochastic Andersen thermostat or Langevin thermostat,
the deterministic Nose-Hoover thermostat or Multiple Anderson thermostats can be used.
See table for the corresponding MDALGO tags.
NVT ensemble Andersen Langevin Nose-Hoover Multiple Andersen
MDALGO 1 3 2 13
additional tags ANDERSEN_PROB LANGEVIN_GAMMA SMASS NSUBSYS, TSUBSYS, PSUBSYS
The user is not allowed to set ISF>2 because then the volume of the simulation would be allowed to change
and the simulation would not result in a NVT ensemble. Setting ISIF=0 will speed up the calculation because the stress
tensor is not computed. The tag IBRION has to be set to zero.