ASE Manual Release 3.6.1.2825 CAMd - CampOS Wiki

Usage
ASE Manual, Release 3.6.1.2828
• The rhombohedral (or trigonal) lattices are not implemented. They will be implemented when the need
arises (and if somebody can tell me the precise definition of the 4-number Miller indices - I only know that
they are “almost the same as in hexagonal lattices”).
• lattice.compounds
Lattices with more than one element. These are mainly intended as examples allowing you to define new
such lattices. Currenly, the following are defined
– B1 = NaCl = Rocksalt
– B2 = CsCl
– B3 = ZnS = Zincblende
– L1_2 = AuCu3
– L1_0 = AuCu
The lattice objects are called with a number of arguments specifying e.g. the size and orientation of the lattice.
All arguments should be given as named arguments. At a minimum the symbol argument must be specified.
symbol The element, specified by the atomic number (an integer) or by the atomic symbol (i.e. ‘Au’). For
compounds, a tuple or list of elements should be given. This argument is mandatory.
directions and/or miller: Specifies the orientation of the lattice as the Miller indices of the three basis
vectors of the supercell (directions=...) and/or as the Miller indices of the three surfaces
(miller=...). Normally, one will specify either three directions or three surfaces, but any combination
that is both complete and consistent is allowed, e.g. two directions and two surface miller indices (this
example is slightly redundant, and consistency will be checked). If only some directions/miller indices are
specified, the remaining should be given as None. If you intend to generate a specific surface, and prefer to
specify the miller indices of the unit cell basis (directions=...), it is a good idea to give the desired
Miller index of the surface as well to allow the module to test for consistency. Example:
>>> atoms = BodyCenteredCubic(directions=[[1,-1,0],[1,1,-1],[0,0,1]],
... miller=[None, None, [1,1,2]], ...)
If neither directions nor miller are specified, the default is directions=[[1,0,0],
[0,1,0], [0,0,1]].
size: A tuple of three numbers, defining how many times the fundamental repeat unit is repeated. Default:
(1,1,1). Be aware that if high-index directions are specified, the fundamental repeat unit may be large.
latticeconstant: The lattice constant. If no lattice constant is specified, one is extracted from
ASE.ChemicalElements provided that the element actually has the crystal structure you are creating. Depending
on the crystal structure, there will be more than one lattice constant, and they are specified by giving
a dictionary or a tuple (a scalar for cubic lattices). Distances are given in Angstrom, angles in degrees.
Structure Lattice constants Dictionary-keys
Cubic a ‘a’
Tetragonal (a, c) ‘a’, ‘c’ or ‘c/a’
Orthorhombic (a, b, c) ‘a’, ‘b’ or ‘b/a’, ‘c’ or ‘c/a’
Triclinic (a, b, c, α, β, γ) ‘a’, ‘b’ or ‘b/a’, ‘c’ or ‘c/a’, ‘alpha’, ‘beta’, ‘gamma’
Monoclinic (a, b, c, alpha) ‘a’, ‘b’ or ‘b/a’, ‘c’ or ‘c/a’, ‘alpha’
Hexagonal (a, c) ‘a’, ‘c’ or ‘c/a’
Example:
>>> atoms = Monoclinic( ... , latticeconstant={’a’: 3.06,
... ’b/a’: 0.95, ’c/a’: 1.07, ’alpha’: 74})
debug: Controls the amount of information printed. 0: no info is printed. 1 (the default): The indices of surfaces
and unit cell vectors are printed. 2: Debugging info is printed.
7.9. Creating atomic structures 95