Bond strengths in solids computed from a Wannier-type construction of local vibrational modes

Abstract

We introduce a Wannier-type formulation of periodic local vibrational mode theory that yields real-space-localized vibrational modes associated with individual internal coordinates in crystalline solids. These modes are constructed as locally coherent superpositions of wavevector-resolved local modes, yielding a smooth and gauge-consistent real-space representation without the need for additional phase-fixing procedures. The resulting Wannier-type local modes provide well-defined force constants and frequencies that enable robust, chemically interpretable measures of bond and interaction strengths in periodic systems. Moreover, our framework demonstrates that phonon dispersion behavior makes important contributions to the bond and interaction strengths calculated via local vibrational mode theory. We demonstrate the method for representative ionic and covalent systems, including MgO, tetrahedrally-coordinated C, Si, SiC, and two polymorphs of CaCO3. Our framework establishes a direct analog of molecular local modes for fully periodic systems and opens new avenues for quantitative bonding analysis in crystalline materials.