Accurate multireference study of Si3 electronic manifold

TL;DR

This study provides a highly accurate multi-reference analysis of Si3, revealing detailed electronic structure, potential energy surfaces, and the significance of inter-system crossings for understanding its reactive dynamics.

Contribution

It offers the first comprehensive multi-reference potential energy surface analysis of Si3, including structures, vibrational constants, energy gaps, and spin-orbit coupling, highlighting the complexity of its electronic states.

Findings

Ground state predicted as singlet with small singlet-triplet gap

Inter-system crossings are crucial in Si3 dynamics

Accurate potential energy surface features are benchmarked

Abstract

Since it has been shown that the silicon trimer has a highly multi-reference character, accurate multi-reference configuration interaction calculations are performed to elucidate its electronic manifold. Emphasis is given to the long range part of the potential, aiming to understand the atom-diatom collisions dynamical aspects, to describe conical intersections and important saddle points along the reactive path. Potential energy surface main features analysis are performed for benchmarking, and highly accurate values for structures, vibrational constants and energy gaps are reported, as well as the unpublished spin-orbit coupling magnitude. The results predict that inter-system crossings will play an important role in dynamical simulations, specially in triplet state quenching, making the problem of constructing a precise potential energy surface more complicated and multi-layer dependent. The ground state is predicted to be the singlet one, but since the singlet-triplet gap is rather small (2.448 kJ/mol) both of them are expected to be populated at room temperature.