Gets a GULP input with Tersoff potential for an oxide structure

        Args:
            structure: pymatgen.core.structure.Structure
            periodic (Default=False): Flag denoting whether periodic
                boundary conditions are used
            library (Default=None): File containing the species and potential.
            uc (Default=True): Unit Cell Flag.
            keywords: GULP first line keywords.

def tersoff_input(self, structure, periodic=False, uc=True, *keywords):
        """
        Gets a GULP input with Tersoff potential for an oxide structure

        Args:
            structure: pymatgen.core.structure.Structure
            periodic (Default=False): Flag denoting whether periodic
                boundary conditions are used
            library (Default=None): File containing the species and potential.
            uc (Default=True): Unit Cell Flag.
            keywords: GULP first line keywords.
        """
        #gin="static noelectrostatics \n "
        gin = self.keyword_line(*keywords)
        gin += self.structure_lines(
            structure, cell_flg=periodic, frac_flg=periodic,
            anion_shell_flg=False, cation_shell_flg=False, symm_flg=not uc
        )
        gin += self.tersoff_potential(structure)
        return gin