cparameters.rst

Unit cell input parameters

• Notes about format
• The unit cell
  • a
  • b
  • c
• Atomic positions
  • direct
  • pos
  • atomtypes
• K-point grid density
  • ksampling

Notes about format

The input files follow normal YAML conventions. Please inspect the sample file :file:`input/cellparam.yml`. Even though many parameters have default values if not specified the user should always run the calculations with fully specified input files for consistency and reproducibility.

The unit cell

a

The first lattice vector describing the unit cell in AA.

b

The second lattice vector describing the unit cell in AA.

c

The third lattice vector describing the unit cell in AA.

Example:

a: [5.0,0.0,0.0]
b: [0.0,5.0,0.0]
c: [0.0,0.0,5.0]

Generates a unit cell that is 5.0 by 5.0 by 5.0 AA.

Atomic positions

direct

Determines if the atomic positions are given in direct coordinates.

Example:

direct: True

The atomic positions are given in direct coordinates

pos

A list of the atomic positions. In direct or cartersian coordinates depending on the parameter direct.

Example:

pos: [[0.0,0.0,0.0]]

One atom centered at origo.

atomtypes

The type of atoms as a list in the same order as pos. Use abbreviations that are standard to the periodic table. An addition element X is added for unknown types.

Example:

atomtypes: [X]

K-point grid density

ksampling

The k-point sampling along each axis of the configured reciprocal unit cell.

Example:

ksampling: [15,15,15]

Use 15 by 15 by 15 samples in the full reciprocal unit cell.