Author: Brandon S Runnels (brunnels@uccs.edu),
        The University of Colorado Colorado Springs
Date: 2019-09-18
Version: 002

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*                       Summary of input variables                           *
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In this Test Driver (TD), the user specifies the following variables through
stdin using a Jinja template file named 'pipeline.stdin.tpl' contained in the
directory of a Test which uses this TD (the sequence in which they are
specified must be the same as below, with 'modelname' being the first):

modelname: str
  Contains the extended-id of a valid KIM Model.  This can be specified by
  '@<MODELNAME >@' in pipeline.stdin.tpl.  When the pipeline mates a Model with
  the Test, it will automatically replace '@< MODELNAME >@' with the Model's
  extended-ID.

a1: list of int
  The three miller indices corresponding to the vector that is initially in the GB
  (along the x direction)

a2: list of int
  The three miller indices corresponding to the vector that is initially normal to
  the GB (along the y direction)

a3: list of int
  The three miller indices corresponding to the tilt direction (along the z
  direction)

  Note: a1, a2, a3 must be mutually orthogonal and must obey the
  right hand rule. Normality is not enforced.

species: str
  The name of the material

short_name: str
  The name of the crystal structure: should be fcc, bcc, or sc

a, cohesive_energy: list of float
  The lattice constant in meters and the cohesive energy must be in Joules.

mass: float
  The molar mass (in g/mol) of the element specified by 'element', e.g. 39.948
  for Argon.

theta_min: float
  The initial tilt angle (in degrees)

theta_max: float
  The final tilt angle (in degrees)

max_denominator: int
  The maximum width (in number of latice spacings) of a repeating unit cell.
  The choice of this variable determines the number of GB orientations that
  will be considered.

cutoff_distance: float
  The threshold for initially deleting atomns. Units are in terms of lattice
  spacings, for instance, a value of 0.5 would delete atoms that are closer
  than 0.5*a.

x_repeat: int
  Number of repeating cells in the x direction

z_repeat: int
  Number of repeating cells in the z direction

min_cell_height: float
  Minimum height of the unit cell (direction normal to interface) in angstroms.
  The number of repeating cells in the y direction is determined based on this
  value.

offset_grid_frac: float
  Once both grains are constructed, a grid search over the different
  translations of one grain relative to the other parallel to the plane of the
  grain boundary is performed.  A static minimization of the atomic positions
  is performed for each two-dimensional offset vector corresponding to a point
  on the grid.  This grid is square, and this parameter defines the edge length
  of the squares of the grid, i.e. it is the distance between any given grid
  point and its four nearest neighboring grid points.  Note that this parameter
  is expressed as a fraction of the lattice parameter; a reasonable value in
  most cases is ~0.25.