Local Vibrational Mode Analysis

Harmonic frequency calculations and normal mode analysis are standard in modern quantum chemistry research. However, normal modes are usually delocalized, which limits their utility in studying individual chemical bonds. In order to gain insight on local chemical bonds, Prof. E. Kraka’s group has developed a software package LMODEA based on the local vibrational mode theory (see WIREs: Comput. Mol. Sci., e1480 (2020)).

  • Local modes are derived from normal modes via mass-decoupled Euler-Lagrange equations. Only the information about force constants and normal modes is needed.

  • The LMODEA package can be easily connected to Q-Chem. After a standard Q-Chem frequency calculation, the generated .fchk file can be read by LMODEA for local mode analysis.

  • Applications of local mode analysis include characterizing covalent bonds, hydrogen bonds, and weak interactions, assigning aromaticity indices, studying chemical similarity, calculation of pKa, and chiral discrimination.