We define the local structure of a non-terminal atom as the relative geometry of the atoms connected to it. The local structure of a given atom can be specified as a set of internal coordinates (distances, angles, and dihedral angles). In this work, we restrict ourselves to molecules that don't have rings as cyclic molecules would require special considerations. Local structures around non-terminal atoms are very constrained and highly dependent on the hybridization of the central atom. For this reason, we use a simple method for generating the local structure of molecules: