ECV_CUSTOM

	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.

Use some given CVs as a set of expansion collective variables (ECVs).

This can be useful e.g. for quickly testing new ECVs, but from a performance point of view it is probably better to implement a new ECV class.

By default the ARGs are expeted to be energies, \(\Delta U_i\), and are then multiplied by the inverse temperature \(\beta\)

\[ \Delta u_i=\beta \Delta U_i\, . \]

Use the DIMENSIONLESS flag to avoid this multiplication.

The flag ADD_P0 adds also the unbiased distribution to the target. It is possible to specify a BARRIER as in ECV_UMBRELLAS_LINE, to avoid a too high initial bias.

Examples

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

ene: ENERGY The ENERGY action with label ene calculates a single scalar value
t1: CUSTOM 
PERIODIC
compulsory keyword 
if the output of your function is periodic then you should specify the periodicity
of the function. 
=NO 
ARG
the input for this action is the scalar output from one or more other actions. 
=ene 
FUNC
compulsory keyword 
the function you wish to evaluate 
=(300/500-1)*x The CUSTOM action with label t1 calculates a single scalar value
t2: CUSTOM 
PERIODIC
compulsory keyword 
if the output of your function is periodic then you should specify the periodicity
of the function. 
=NO 
ARG
the input for this action is the scalar output from one or more other actions. 
=ene 
FUNC
compulsory keyword 
the function you wish to evaluate 
=(300/1000-1)*x The CUSTOM action with label t2 calculates a single scalar value
ecv: ECV_CUSTOM 
ARG
compulsory keyword 
the labels of the single ECVs. 
=t1,t2 
TEMP
compulsory keyword ( default=-1 )
temperature. 
=300 
ADD_P0
 could not find this keyword 
 The ECV_CUSTOM action with label ecv calculates the following quantities:

 Quantity   
 Description  
ecv.t1
the label of this action is set by user in the input. See documentation above.
ecv.t2
the label of this action is set by user in the input. See documentation above.


opes: OPES_EXPANDED 
ARG
compulsory keyword 
the label of the ECVs that define the expansion. 
=ecv.* 
PACE
compulsory keyword 
how often the bias is updated 
=500 The OPES_EXPANDED action with label opes calculates a single scalar value

It is equivalent to the following:

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

ene: ENERGY The ENERGY action with label ene calculates a single scalar value
ecv: ECV_MULTITHERMAL 
ARG
compulsory keyword 
the label of the internal energy of the system. 
=ene 
TEMP
compulsory keyword ( default=-1 )
temperature. 
=300 
TEMP_SET_ALL
manually set all the temperatures 
=300,500,1000 The ECV_MULTITHERMAL action with label ecv calculates a single scalar value
opes: OPES_EXPANDED 
ARG
compulsory keyword 
the label of the ECVs that define the expansion. 
=ecv.* 
PACE
compulsory keyword 
how often the bias is updated 
=500 The OPES_EXPANDED action with label opes calculates a single scalar value

Glossary of keywords and components

Compulsory keywords

TEMP	( default=-1 ) temperature. If not specified tries to get it from MD engine
ARG	the labels of the single ECVs. \(\Delta U_i\), in energy units

Options

NUMERICAL_DERIVATIVES	( default=off ) calculate the derivatives for these quantities numerically
ADD_P0	( default=off ) add the unbiased Boltzmann distribution to the target distribution, to make sure to sample it
DIMENSIONLESS	( default=off ) consider ARG as dimensionless rather than an energy, thus do not multiply it by \(\beta\)
BARRIER	a guess of the free energy barrier to be overcome (better to stay higher than lower)