The $variation block

The $variation block sets up the variations (see Parameter-search Grid). This block can appear multiple times in the input file.

The input parameters that are set in this block are listed below.

Block parameters

Parameter	Value Type	Description	Remarks
name	string	The name for the variation object.	The main variation must be named main.
type	string	The type of the variation object. The allowed values are cartesian, coupled and explicit.
pars	List[string]	The names of the parameters associated with the variation (see Interaction Parameters).	Atomtype parameter names can optionally be followed by include INCL and/or exclude EXCL, where INCL and EXCL are the pairs_include and pairs_exclude regular expressions, respectively (see Atomtype Parameters).

Type cartesian

Parameter	Value Type	Description	Remarks
function	List[expression]	(Optional) A list of mathematical expressions that correspond to the components of the enhanced-cartesian-variation scaling function (see Cartesian Variation).	Each expression accepts numbers, the usual operations +,-,*,/,** as well as the functions exp and log. The original components of a variation member can be referred to as x[0], x[1], etc. The expressions cannot contain spaces.
start	List[numerical]	The components of the cartesian-variation origin.
step	List[numerical]	The components of the cartesian-variation step.
size	List[numerical]	The dimensions of the cartesian variation.

Type coupled

Parameter	Value Type	Description	Remarks
using	object reference	The name of the variation to which the variation at hand is coupled.	Depends on the variation to which it refers.
function	List[expression]	The list of mathematical expressions that correspond to the components of the coupling function (see Coupled Variation).	Each expression accepts numbers, the usual operations +,-,*,/,** as well as the functions exp and log. The original components of a variation member can be referred to as x[0], x[1], etc. The expressions cannot contain spaces.

Type explicit

Parameter	Value Type	Description	Remarks
dim	numerical	The number of dimensions of the grid members, i.e. how many parameters are defined by each grid point.	This value must match with the number of parameters specified in the pars option.
values	List[numerical]	The explicit parameter values associated with each grid member. The values are read in batches of size dim for each grid point.	The resulting grid is uni-dimensional with size equal to the number of entries divided by dim.

Note

Parameters that are not listed above can also be supplied. They are not recognized by the program in any special way, but are parsed and made available in the Customization API, together with all the other block parameters, as an InputParameters object.

Example

See Tutorial for a commented example.