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. | ||
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the deterministic [[Nose-Hoover thermostat]] or [[MDALGO#MDALGO.3D13:_Multiple_Anderson_thermostats|Multiple Anderson thermostats]] can be used. | the deterministic [[Nose-Hoover thermostat]] or [[MDALGO#MDALGO.3D13:_Multiple_Anderson_thermostats|Multiple Anderson thermostats]] can be used. | ||
See table for the corresponding {{TAG|MDALGO}} tags. | See table for the corresponding {{TAG|MDALGO}} tags. | ||
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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. | and the simulation would not result in a NVT ensemble. | ||
Other flags related to molecular dynamics simulations can be found [[Molecular dynamics calculations|here]]. | Other flags related to molecular dynamics simulations can be found [[Molecular dynamics calculations|here]]. | ||
''A simple example INCAR file for the [[Langevin thermostat]] could look like''' | ''A simple example INCAR file for the [[Langevin thermostat]] could look like''' | ||
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POTIM = 1.0 # time step in femto seconds | POTIM = 1.0 # time step in femto seconds | ||
LANGEVIN_GAMMA = 10.0 10.0 # setting friction coefficient in inverse time units | LANGEVIN_GAMMA = 10.0 10.0 # setting friction coefficient in inverse time units | ||
Note this {{FILE|INCAR}} file only contains the parameters for the molecular dynamics part. The | Note this {{FILE|INCAR}} file only contains the parameters for the molecular dynamics part. The | ||
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{{FILE|REPORT}}, [[Molecular dynamics calculations]] | {{FILE|REPORT}}, [[Molecular dynamics calculations]] | ||
[[Category:Molecular dynamics]][[Category:Ensembles]][[Category:Thermostats | [[Category:Molecular dynamics]][[Category:Ensembles]][[Category:Thermostats]] | ||
Revision as of 14:01, 19 July 2022
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. Other flags related to molecular dynamics simulations can be found here.
A simple example INCAR file for the Langevin thermostat could look like'
#INCAR molecular dynamics tags NVT ensemble IBRION = 0 # choose molecular dynamics MDALGO = 3 # using Langevin thermostat ISIF = 2 # compute stress tensor but do not change box volume/shape TEBEG = 300 # set temperature NSW = 10000 # number of time steps POTIM = 1.0 # time step in femto seconds LANGEVIN_GAMMA = 10.0 10.0 # setting friction coefficient in inverse time units
Note this INCAR file only contains the parameters for the molecular dynamics part. The electronic minimization or the machine learning tags have to be added.