What is HDNNP?

This program is an implementation of HDNNP that is suggested by Behler et al [Ref].
HDNNP stands for High Dimensional Neural Network Potential.
HDNNP is one of machine learning potentials that is used to reduce calculation cost of DFT(Density Functional Theory) calculation.
Currently, energy and force prediction using symmetry function have been implemented.
[Ref]https://onlinelibrary.wiley.com/doi/full/10.1002/qua.24890