Theoretical studies of homo and heteronuclear diatomic molecules

Author(s)

João Paulo Gobbo

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2009-09-11

Examining board members

Antonio Carlos Borin; Rogério Custódio; Nelson Henrique Morgon; Mauro Carlos Costa Ribeiro; Peter Wilhelm Tiedemann

• Advisor: Antonio Carlos Borin

Abstract

In this work, high level ab initio multiconfigurational methods with extensive basis set and inclusion of relativistic e¤ects were employed to study several diatomic systems containing transition metals. The Multiconfiguration Second Order Perturbation Theory (CASPT2) or its Multi-State version (MS-CASPT2) approaches, based on Complete- Active-Space Self-Consistent-Field (CASSCF), were employed, with the Atomic Natural Orbital contracted in a relativistic environment (ANO-RCC) with quadruple- quality, in order to study these systems. In relation to the homonuclear dimers of transition metals atoms (Re2, Tc2, Ta2, Mo2, and W2), we have characterized their ground state and several excited states through potential energy curves, spectroscopic constants and e¤ective bond orders. All dimers we studied have the multiplicity of the chemical bond above four. To these kind of systems, we have also studied the splitting caused by spin-orbit coupling with the the aim of determine the symmetry of the ground state and help in the interpretation of the experimental spectras. About the diatomic formed by joining of a transition metal atom and an atom of the main group, we have focused, mainly, the transition metal nitrites and borides (CoN, MnN, TcN, and RhB) In the same way, these systems were described in terms of their potential energy curves, spectroscopic constants and wavefunctions and we have com- pared to other theoretical and experimental results. All molecules studied in this part were characterized as triple bonded, with a pair of electrons on the non–metalic center and the remaining electrons localized on the metal, coupled on di¤erent forms (AU)