MATHEVAL

This is part of the function module

An alias to the CUSTOM function.

This alias is kept in order to maintain compatibility with previous PLUMED versions. However, notice that as of PLUMED 2.5 the libmatheval library is not linked anymore, and the MATHEVAL function is implemented using the Lepton library.

Examples

Just replace CUSTOM with MATHEVAL.

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

contract shortcuts

d: DISTANCE 
ATOMS
the pair of atom that we are calculating the distance between. 
=10,15 The DISTANCE action with label d calculates a single scalar value
m: MATHEVAL 
ARG
the input to this function. 
=d 
FUNC
compulsory keyword 
the function you wish to evaluate 
=0.5*step(0.5-x)+x*step(x-0.5) 
PERIODIC
compulsory keyword 
if the output of your function is periodic then you should specify the periodicity
of the function. 
=NO The MATHEVAL action with label m calculates a single scalar value
# check the function you are applying:
PRINT 
ARG
the input for this action is the scalar output from one or more other actions. 
=d,m 
FILE
the name of the file on which to output these quantities 
=checkme The PRINT action with label 
RESTRAINT 
ARG
the arguments on which the bias is acting. 
=d 
AT
compulsory keyword 
the position of the restraint 
=0.5 
KAPPA
compulsory keyword ( default=0.0 )
specifies that the restraint is harmonic and what the values of the force constants
on each of the variables are 
=10.0 The RESTRAINT action with label 

d: DISTANCE 
ATOMS
the pair of atom that we are calculating the distance between. 
=10,15 The DISTANCE action with label d calculates a single scalar value
m: MATHEVAL_SCALAR 
ARG
the input for this action is the scalar output from one or more other actions. 
=d 
FUNC
compulsory keyword 
the function you wish to evaluate 
=0.5*step(0.5-x)+x*step(x-0.5) 
PERIODIC
compulsory keyword 
if the output of your function is periodic then you should specify the periodicity
of the function. 
=NO The MATHEVAL_SCALAR action with label m calculates a single scalar value
# check the function you are applying:
PRINT 
ARG
the input for this action is the scalar output from one or more other actions. 
=d,m 
FILE
the name of the file on which to output these quantities 
=checkme The PRINT action with label 
@5: RESTRAINT_SCALAR 
ARG
the input for this action is the scalar output from one or more other actions. 
=d 
AT
compulsory keyword 
the position of the restraint 
=0.5 
KAPPA
compulsory keyword ( default=0.0 )
specifies that the restraint is harmonic and what the values of the force constants
on each of the variables are 
=10.0 The RESTRAINT_SCALAR action with label @5 calculates the following quantities:

 Quantity   
 Description  
@5.bias
the instantaneous value of the bias potential
@5.force2
the instantaneous value of the squared force due to this bias potential

(see also DISTANCE, PRINT, and RESTRAINT)

Glossary of keywords and components

Compulsory keywords

PERIODIC	if the output of your function is periodic then you should specify the periodicity of the function. If the output is not periodic you must state this using PERIODIC=NO
FUNC	the function you wish to evaluate

Options

ARG	the input to this function. You can use multiple instances of this keyword i.e. ARG1, ARG2, ARG3...
VAR	the names to give each of the arguments in the function. If you have up to three arguments in your function you can use x, y and z to refer to them. Otherwise you must use this flag to give your variables names.