where η A and R A s have the same role to modify the width and location of radial Gaussian functions, and the parameters ζ and θ s control the width and location of different angular regions. Note that these angular functions are the modified versions of original Behler-Parinello symmetry functions and reflect the changes made by Smith et al. Using multiple values of η R , R R s , η A , R A s , θ s and ζ enables us construct a set of symmetry functions that can describe the local environment of an atom in high detail.