Electronic structure and chemical bonding of the MoBe molecule.

Molybdenum beryllium materials are being researched and applied in cutting-edge technologies. It has been found that beryllium, even though it has a full 2s subshell, can form a variety of bonds with specific atoms. Here, the simple building block, the MoBe molecule, is investigated to shed light in their bonding. Specifically, forty-three low-lying states of MoBe have been investigated via complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCISD(+Q)) using the aug-cc-pV5Z(-PP) basis set. Dissociation energies (De), dipole moments, and various spectroscopic constants are calculated, while potential energy curves are plotted. A variety of bonding is formed in MoBe, i.e., half bonds up to the formation of triple bonds, while in most cases, Be atoms are excited at the Be(3P) state. The ground state, X7Σ+, is well separated from the excited ones, i.e., the first excited state, a5Σ+, is lying 15.0 kcal mol-1 above. The adiabatic De of calculated states range from 2.5 (9Σ+(1), van der Waals interaction) to 57.7 kcal mol-1 (b5Π). The b5Π, 3Δ(1), and 3Π(1) have triple bonds, while their diabatic De values are 86.7, 92.0 and 88.0 kcal mol-1. The MRCISD+Q bond distances range from 2.047 (3Δ(1)) to 2.787 Å (9Σ+(1)), while dipole moments range from 1.51 to 3.28 D. Overall, the present work highlights the exceptional ability of beryllium atoms to participate in a variety of bonding schemes, and it could provide the opening gate for further investigation of this species or associated materials and complexes.