begin{data} begins data block.
All files must begin with this entry.
begin{lattice} begins lattice block data.
a0{x} defines lattice parameter.
x is a real number
vec{x y z} defines primitive vector
ai of coordinates (x, y, z) in
a0 units.
This line must be repeated three times for
a1, a2,
and a3
primitive vectors respectively.
end{lattice} ends lattice block data.
begin{structure} begins structural data in each unit cell
type x y zwhere type is an integer, and x, y, and z are the atom coordinates in a0 units.
end{strucutre} ends structural data block
scale{l m n} defines the supercell
scaling factors l, m and
n in a1, a2 and
a3 directions respectively. These numbers should be
integers. For example, if we want a supercell of 3x3x2=18 unit cells,
this entry should be scale{3 3 2}.
onion{l m n} creates a supercell with
scaling factors defined in scaleand chops a subset of atoms defined by a supercell of scaling l m n.
origin{centre / x y z} defines the origin
of coordinates. centre option
should be included if we want the origin to be the geometrical centre
of the supercell. Optionally, it can be chosen some particular
point (x,y,z) in a0 units.
cutoff{x} Defines the cutoff radius when
chosing the nearest neibours.
x is a real number in a0 units.
For Td or Oh crystals,
chose.cutoff{0.7}
end{data} ends data block.
All files must end with this entry.The following lines contain an example dat.scg file which generates a 3x3x3 fcc silicon supercell. The origin of axis is the geometrical centre of the supercell. Note that in this case we chose a0 in atomic units.
%
% dat.scg input file
%
begin{data}
begin{lattice}
a0{10.266666666}
vec{0.5 0.5 0.0}
vec{0.5 0.0 0.5}
vec{0.0 0.5 0.5}
end{lattice}
scale{3 3 3}
cutoff{0.7}
origin{centre}
begin{structure}
1 0.0 0.0 0.0
1 0.25 0.25 0.25
end{structure}
end{data}