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

contract shortcuts

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
compulsory keyword 
the values input to this function 
=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
compulsory keyword 
the values input to this function 
=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 value of the argument named t1
ecv.t2
the value of the argument named t2


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

ene: ENERGY The ENERGY action with label ene 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
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

Description of components

The names of the components in this action can be customized by the user in the actions input file. However, in addition to the components that can be customized the following quantities will always be output


 Quantity   
 Description    

 .#!custom  
the names of the output components for this action depend on the actions input file see the example inputs below for details   

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)