Input Nodes

[brian.w....@gmail.com]

Hi All,

I was wondering how the number of Input nodes are calculated based on the Chebychev parameters. I noticed as I increased the polynomial order of either the angular or radial functions, the number of input nodes would increase, but I haven't figured out how the number of input nodes are calculated. Any help is appreciated!

Best,

Brian Doherty

[Nongnuch Artrith]

Hi Brian,

You are right that the number of input nodes depends on the order of the Chebyshev expansion, i.e., the dimension of the descriptor of the local atomic environment.  An order of N (sum of radial and angular order) means N+1 Chebyshev polynomials are used in the expansion since the lowest order is 0.  For a system with just one chemical species, the descriptor then has a dimension of N+1 which is the number of input nodes.  For multicomponent systems, i.e., compositions with multiple chemical elements, the dimension is 2*(N+1) and half of the descriptor encodes the atomic species.

This is described in more detail in Phys. Rev. B 96 (2017) 014112 (http://dx.doi.org/10.1103/PhysRevB.96.014112).

Best,
Nong

[brian.w....@gmail.com]

Great makes much more sense. Thank you!