Supercell: Difference between revisions

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[[File:SupercellExample.png|200px|thumb|right|Example with 2 unit cells in c-direction, created with: supercell 1,1,2,2x19,withmates=1]]
{{Infobox psico
|module    = psico.xtal
}}


= Overview =
[[File:SupercellExample.png|200px|thumb|right|Example with 2 unit cells in c-direction, created with: supercell 1,1,2,2x19]]


Can display multiple copies of the unit cell.
'''supercell''' can display multiple copies of the unit cell.
Can also fill the unit cell (and its copies) with symmetry mates.
Can also fill the unit cell (and its copies) with symmetry mates.


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Requires [http://numpy.scipy.org numpy].
Requires [http://numpy.scipy.org numpy].


= Example =
== Example ==


<source lang="python">
<source lang="python">
run supercell.py
# import psico.xtal, or run the standalone script:
run https://raw.githubusercontent.com/speleo3/pymol-psico/master/psico/xtal.py
 
fetch 2x19, async=0
fetch 2x19, async=0
supercell 2,1,1, 2x19, green
supercell 2,1,1, 2x19, green
supercell 1,1,2, 2x19, orange, name=super2
supercell 1,1,2, 2x19, orange, name=super2
supercell 1,1,2, 2x19, orange, name=super2, withmates=1
</source>
</source>


= The Code =
== See Also ==
 
<source lang="python">
'''
(c) 2010 Thomas Holder
 
PyMOL python script (load with `run supercell.py`)
Usage: See "help supercell" and "help symexpcell"
'''
 
from pymol import cmd, cgo, xray
from math import cos, sin, radians, sqrt
import numpy
 
def cellbasis(angles, edges):
'''
For the unit cell with given angles and edge lengths calculate the basis
transformation (vectors) as a 4x4 numpy.array
'''
rad = [radians(i) for i in angles]
basis = numpy.identity(4)
basis[0][1] = cos(rad[2])
basis[1][1] = sin(rad[2])
basis[0][2] = cos(rad[1])
basis[1][2] = (cos(rad[0]) - basis[0][1]*basis[0][2])/basis[1][1]
basis[2][2] = sqrt(1 - basis[0][2]**2 - basis[1][2]**2)
edges.append(1.0)
return basis * edges # numpy.array multiplication!
 
def supercell(a=1, b=1, c=1, object=None, color='blue', name='supercell', withmates=0):
'''
DESCRIPTION
 
    Draw a supercell, as requested by Nicolas Bock on the pymol-users
    mailing list (Subject: [PyMOL] feature request: supercell construction
    Date: 04/12/2010 10:12:17 PM (Mon, 12 Apr 2010 14:12:17 -0600))
 
USAGE
 
    supercell a, b, c [, object [, color [, name [, withmates]]]]


ARGUMENTS
* [[SuperSym]]
 
* [[symexp]]
    a, b, c = integer: repeat cell in x,y,z direction a,b,c times
    {default: 1,1,1}
 
    object = string: name of object to take cell definition from
 
    color = string: color of cell {default: blue}
 
    name = string: name of the cgo object to create {default: supercell}
 
    withmates = bool: also create symmetry mates in displayed cells
    {default: 0}
 
SEE ALSO
 
    show cell
 
'''
if object is None:
object = cmd.get_object_list()[0]
withmates = int(withmates)
 
sym = cmd.get_symmetry(object)
cell_edges = sym[0:3]
cell_angles = sym[3:6]
 
basis = cellbasis(cell_angles, cell_edges)
assert isinstance(basis, numpy.ndarray)
 
ts = list()
for i in range(int(a)):
for j in range(int(b)):
for k in range(int(c)):
ts.append([i,j,k])
 
obj = [
cgo.BEGIN,
cgo.LINES,
cgo.COLOR,
]
obj.extend(cmd.get_color_tuple(color))
for t in ts:
shift = basis[0:3,0:3] * t
shift = shift[:,0] + shift[:,1] + shift[:,2]
for i in range(3):
vi = basis[0:3,i]
vj = [
numpy.array([0.,0.,0.]),
basis[0:3,(i+1)%3],
basis[0:3,(i+2)%3],
basis[0:3,(i+1)%3] + basis[0:3,(i+2)%3]
]
for j in range(4):
obj.append(cgo.VERTEX)
obj.extend((shift + vj[j]).tolist())
obj.append(cgo.VERTEX)
obj.extend((shift + vj[j] + vi).tolist())
 
if withmates:
symexpcell('m%d%d%d_' % tuple(t), object, *t)
 
obj.append(cgo.END)
 
cmd.delete(name)
cmd.load_cgo(obj, name)
 
def symexpcell(prefix='mate', object=None, a=0, b=0, c=0):
'''
DESCRIPTION
 
    Creates all symmetry-related objects for the specified object that
    occur with their bounding box center within the unit cell.
 
USAGE
 
    symexpcell prefix, object, [a, b, c]
 
ARGUMENTS
 
    prefix = string: prefix of new objects
 
    object = string: object for which to create symmetry mates
 
    a, b, c = integer: create neighboring cell {default: 0,0,0}
 
SEE ALSO
 
    symexp
'''
if object is None:
object = cmd.get_object_list()[0]
 
sym = cmd.get_symmetry(object)
cell_edges = sym[0:3]
cell_angles = sym[3:6]
spacegroup = sym[6]
 
basis = cellbasis(cell_angles, cell_edges)
basis = numpy.matrix(basis)
 
extent = cmd.get_extent(object)
center = sum(numpy.array(extent)) * 0.5
center = numpy.matrix(center.tolist() + [1.0]).T
center_cell = basis.I * center
 
extra_shift = [[float(i)] for i in (a,b,c)]
 
i = 0
matrices = xray.sg_sym_to_mat_list(spacegroup)
for mat in matrices:
i += 1
 
mat = numpy.matrix(mat)
shift = numpy.floor(mat * center_cell)
mat[0:3,3] -= shift[0:3,0]
mat[0:3,3] += extra_shift
 
mat = basis * mat * basis.I
mat_list = list(mat.flat)
 
name = '%s%d' % (prefix, i)
cmd.create(name, object)
cmd.transform_object(name, mat_list)
cmd.color(i+1, name)
 
cmd.extend('symexpcell', symexpcell)
cmd.extend('supercell', supercell)
</source>


[[Category:Script_Library]]
[[Category:Script_Library]]
[[Category:Math_Scripts]]
[[Category:Math_Scripts]]

Latest revision as of 04:24, 1 July 2020

Included in psico
This command or function is available from psico, which is a PyMOL extension.

Module psico.xtal
Example with 2 unit cells in c-direction, created with: supercell 1,1,2,2x19

supercell can display multiple copies of the unit cell. Can also fill the unit cell (and its copies) with symmetry mates.

See thread on pymol-users mailing list.

Requires numpy.

Example

# import psico.xtal, or run the standalone script:
run https://raw.githubusercontent.com/speleo3/pymol-psico/master/psico/xtal.py

fetch 2x19, async=0
supercell 2,1,1, 2x19, green
supercell 1,1,2, 2x19, orange, name=super2

See Also

Retrieved from "https://pymolwiki.org/index.php?title=Supercell&oldid=13313"