Identify the CP plane

[qzhu2017]

It is somewhat related to
https://pubs.rsc.org/en/content/articlelanding/2018/CE/c8ce00454d

Will check if it is easy to implement so that we don't need to rebuild the wheel.

@kevinparrish1 Can you help on this? Is it possible to quickly implement it into PyXtal without using CSD_Python?

[qzhu2017]

The initial support for molecular crystal has been implemented
It takes the following steps:

• look at the sublattice of molecular center
• Search for the likely (hkl) planes with high density
  -- Loop over all (hkl) within a given cutoff,
  -- for each simple (hkl) direction, gradually increase the multiplicity from 1 to n,
  -- find the first n that returns a structure factor > 0.5 of the total number of atoms
• compute the separation between the molecular layers for each (hkl)
  -- Loop over each (hkl)
  -- compute the molecular slab (center, lower, upper) along the d_hkl
  -- group the molecular slabs by center positions, identify each group (center, lower, upper)
  -- Compute the slab separations

Todo next

• work on Cut the plane function support #208, extract the molecular slab by (hkl)
• Compute the atomic crystals by considering the sublattice of some elements (most heavy or most symmetric site)?
• The goal is to find the widest separation.

[qzhu2017]

 UCECAG03
( 3  3  3) Spacing:  2.124 Separation:  2.166
( 6  6  0) Spacing:  1.181 Separation:  1.540
UCECAG03 MillerIndices(1, 1, 1) 6.372 1.262
UCECAG03 MillerIndices(1, 1, 0) 7.086 0.84

Impossible to get a separation bigger than the d_spacing.

[qzhu2017]

Should work now.