The basic PEECM settings are defined in the $embed block.
It can be redirected to an external file using $embed file=
SPMlt;file_name>;.
Following keywords are used for the PEECM calculation setup:
periodicSpecifies the number of periodic directions. Allowed values for
number
are 3 for a bulk three-dimensional system, 2 for
a two-dimensional surface slab, and 1 for a one-dimensional system. Default
value is 3.
cellUnit cell parameters in a form of six real values | a| , | b| , | c| , α , β , γ , where | a| , | b| , | c| are lengths of the appropriate cell vectors, α is the angle between vectors b and c, β is the angle between vectors a and c, and γ is the angle between vectors a and b. Default are atomic units and degrees. You can specify unit cell parameters in Å and degrees using
cell ang
.
content label x y z endContent of the unit cell, where
label
is the label of the point charge
Content of the unit cell, where label
is the label of the point charge
type and x y z
are corresponding Cartesian or fractional crystal coordinates.
Defaults are Cartesian coordinates and atomic units. You can specify Cartesian
coordinates in Å using content ang
and fractional coordinates using
content frac
. Note that Cartesian coordinates assume that the cell
vector a is aligned along the x
axis, and the vector b on the
xy
plane.
cluster label x y z endAtomic coordinates of the piece of the crystal to be replaced by the QM cluster and surrounding isolation shell (ECPs and explicit point charges), where
label
is
the point charge label and x y z
are corresponding Cartesian or fractional
crystal coordinates. Defaults are Cartesian coordinates and atomic units. You can
specify Cartesian coordinates in Å using cluster ang
and fractional
coordinates using cluster frac
.
charges label charge endValues of point charges (for each atom-type) , where
label
is the point charge label and
charge
specifies charge in atomic units.
ch_list label charge endValues of point charges (for each atom), where
label
is the point charge label and
charge
specifies charge in atomic units.
Note that charges
and ch_list
are mutually exclusive.
An integer number n
can also be
appended to charges
or ch_list
to set the
tolerance for charge neutrality violation to 10^{-n}
(default n = 5
).
Additionally, the following keywords control the accuracy of PEECM calculation: