ECV_LINEAR

This is part of the opes module | |

It is only available if you configure PLUMED with ./configure –enable-modules=opes . Furthermore, this feature is still being developed so take care when using it and report any problems on the mailing list. |

Linear expansion, according to a parameter lambda.

This can be used e.g. for thermodynamic integration, or for multibaric simulations, in which case lambda=pressure. It can also be used for multithermal simulations, but for simplicity it is more convenient to use ECV_MULTITHERMAL.

The difference in Hamiltonian \(\Delta U\) is expected as ARG.

\[ \Delta u_\lambda=\beta \lambda \Delta U\, . \]

Use the DIMENSIONLESS flag to avoid multiplying for the inverse temperature \(\beta\).

By defauly the needed steps in lambda are automatically guessed from few initial unbiased MD steps, as descibed in [70]. Otherwise one can set this number with LAMBDA_STEPS. In both cases the steps will be uniformly distriuted. Finally, one can use instead the keyword LAMBDA_SET_ALL and explicitly provide each lambda value.

- Examples

Typical multibaric simulation:

Click on the labels of the actions for more information on what each action computes

vol:VOLUMEecv:ECV_LINEAR ...ARG=compulsory keywordthe label of the Hamiltonian difference \f$\Delta U\f$volTEMP=300compulsory keyword ( default=-1 )temperature.LAMBDA=0.06022140857*2000 #2 kbarcompulsory keyword ( default=0 )the lambda at which the underlying simulation runsLAMBDA_MIN=0.06022140857 #1 bar( default=0 ) the minimum of the lambda rangeLAMBDA_MAX=0.06022140857*4000 #4 kbar ...( default=1 ) the maximum of the lambda rangeopes:OPES_EXPANDEDARG=compulsory keywordthe label of the ECVs that define the expansion.ecv.volPACE=500compulsory keywordhow often the bias is updated

Typical thermodynamic integration:

Click on the labels of the actions for more information on what each action computes

DeltaU:EXTRACVNAME=energy_differencecompulsory keywordname of the CV as computed by the MD engineecv:ECV_LINEARARG=compulsory keywordthe label of the Hamiltonian difference \f$\Delta U\f$DeltaUTEMP=300compulsory keyword ( default=-1 )temperature.opes:OPES_EXPANDEDARG=compulsory keywordthe label of the ECVs that define the expansion.ecv.*PACE=100compulsory keywordhow often the bias is updated

Notice that by defauly LAMBDA=0, LAMBDA_MIN=0 and LAMBDA_MAX=1, which is the typical case for thermodynamic integration.

- Glossary of keywords and components

- Compulsory keywords

TEMP | ( default=-1 ) temperature. If not specified tries to get it from MD engine |

ARG | the label of the Hamiltonian difference \(\Delta U\) |

LAMBDA | ( default=0 ) the lambda at which the underlying simulation runs |

- Options

NUMERICAL_DERIVATIVES | ( default=off ) calculate the derivatives for these quantities numerically |

DIMENSIONLESS | ( default=off ) ARG is considered dimensionless rather than an energy, thus is not multiplied by \(\beta\) |

GEOM_SPACING | ( default=off ) use geometrical spacing in lambda instead of linear spacing |

LAMBDA_MIN | ( default=0 ) the minimum of the lambda range |

LAMBDA_MAX | ( default=1 ) the maximum of the lambda range |

LAMBDA_STEPS | uniformly place the lambda values, for a total of LAMBDA_STEPS |

LAMBDA_SET_ALL | manually set all the lamdbas |