Application of the Energy Derivative Analysis Method to the Cis Monobridged Equilibrium Structures Al2H2, Si2H2, Ga2H2, and Ge2H2 and the Comparable Stationary Points of B2H2 and C2H2

An energy derivative analysis method for closed-shell self-consistent field (SCF) wave functions has been applied to the newly (theoretically and/or experimentally) discovered cis monobridged compounds Al₂H₂, Si₂H₂, Ga₂H₂, and Ge₂H₂. Monobridged stationary points for the B₂H₂and C₂H₂molecules were also considered for comparative purposes. At the stationary points, the first and second derivatives of the orbital, electronic, nuclear, and total energies for SCF wave functions were transformed from the Cartesian to the normal coordinate and to the mass-weighted normal coordinate systems. The energy derivative quantities in terms of the molecular vibrations provide crucial information concerning the structural stability of the monobridged dihydrides of group IIIA and group IVA atoms.