LWALLS

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

Add LOWER_WALLS restraints on all the multicolvar values

This action takes the set of values calculated by the colvar specified by label in the DATA keyword and places a restraint on each quantity, \(x\), with the following functional form:

\( k((x-a+o)/s)^e \)

\(k\) (KAPPA) is an energy constant in internal unit of the code, \(s\) (EPS) a rescaling factor and \(e\) (EXP) the exponent determining the power law. By default: EXP = 2, EPS = 1.0, OFF = 0.

Examples

The following set of commands can be used to stop any of the 800 atoms in group A from moving more than 2.46425 nm in the z direction from atom 34137. This is done by adding a lower wall on the z-distance between all the atoms in group A and the position of 34137.

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

l: ZDISTANCES 
GROUPA
Calculate the distances between all the atoms in GROUPA and all the atoms in GROUPB.
=1-800 
GROUPB
Calculate the distances between all the atoms in GROUPA and all the atoms in GROUPB.
=34137 
NOPBC
( default=off ) ignore the periodic boundary conditions when calculating distances
 The ZDISTANCES action with label l
lwall: LWALLS 
DATA
compulsory keyword 
certain actions in plumed work by calculating a list of variables and summing over
them. 
=l 
AT
compulsory keyword 
the radius of the sphere 
=2.46465 
KAPPA
compulsory keyword 
the force constant for the wall. 
=150.0 
EXP
compulsory keyword ( default=2.0 )
the powers for the walls. 
=2 
EPS
compulsory keyword ( default=1.0 )
the values for s_i in the expression for a wall 
=1 
OFFSET
compulsory keyword ( default=0.0 )
the offset for the start of the wall. 
=0 The LWALLS action with label lwall calculates a single scalar value

Glossary of keywords and components

Description of components

By default the value of the calculated quantity can be referenced elsewhere in the input file by using the label of the action. Alternatively this Action can be used to calculate the following quantities by employing the keywords listed below. These quantities can be referenced elsewhere in the input by using this Action's label followed by a dot and the name of the quantity required from the list below.

Quantity	Description
bias	the instantaneous value of the bias potentials

In addition the following quantities can be calculated by employing the keywords listed below

Quantity	Keyword	Description
gradient	GRADIENT	the gradient
vmean	VMEAN	the norm of the mean vector. The output component can be referred to elsewhere in the input file by using the label.vmean
vsum	VSUM	the norm of sum of vectors. The output component can be referred to elsewhere in the input file by using the label.vsum
spath	SPATH	the position on the path
gspath	GPATH	the position on the path calculated using trigonometry
gzpath	GPATH	the distance from the path calculated using trigonometry
zpath	ZPATH	the distance from the path
altmin	ALT_MIN	the minimum value. This is calculated using the formula described in the description of the keyword so as to make it continuous.
between	BETWEEN	the number/fraction of values within a certain range. This is calculated using one of the formula described in the description of the keyword so as to make it continuous. You can calculate this quantity multiple times using different parameters.
highest	HIGHEST	the highest of the quantities calculated by this action
lessthan	LESS_THAN	the number of values less than a target value. This is calculated using one of the formula described in the description of the keyword so as to make it continuous. You can calculate this quantity multiple times using different parameters.
lowest	LOWEST	the lowest of the quantities calculated by this action
max	MAX	the maximum value. This is calculated using the formula described in the description of the keyword so as to make it continuous.
mean	MEAN	the mean value. The output component can be referred to elsewhere in the input file by using the label.mean
min	MIN	the minimum value. This is calculated using the formula described in the description of the keyword so as to make it continuous.
moment	MOMENTS	the central moments of the distribution of values. The second moment would be referenced elsewhere in the input file using label.moment-2, the third as label.moment-3, etc.
morethan	MORE_THAN	the number of values more than a target value. This is calculated using one of the formula described in the description of the keyword so as to make it continuous. You can calculate this quantity multiple times using different parameters.
sum	SUM	the sum of values

Compulsory keywords

DATA	certain actions in plumed work by calculating a list of variables and summing over them. This particular action can be used to calculate functions of these base variables or prints them to a file. This keyword thus takes the label of one of those such variables as input.
AT	the radius of the sphere
KAPPA	the force constant for the wall. The k_i in the expression for a wall.
OFFSET	( default=0.0 ) the offset for the start of the wall. The o_i in the expression for a wall.
EXP	( default=2.0 ) the powers for the walls. The e_i in the expression for a wall.
EPS	( default=1.0 ) the values for s_i in the expression for a wall

Options

NUMERICAL_DERIVATIVES	( default=off ) calculate the derivatives for these quantities numerically
SERIAL	( default=off ) do the calculation in serial. Do not use MPI
LOWMEM	( default=off ) lower the memory requirements
TIMINGS	( default=off ) output information on the timings of the various parts of the calculation