Accurate Electrical and Spectroscopic Properties of X(1)Sigma(+) BeO from Coupled-Cluster Methods

摘要

This paper reports a Series of coupled-cluster (CC) calculations through CCSDT onthe theoretically challenging ground state of the BeO molecule. Along with CC methods quadratic configuration interaction (Qa) approximations to CC theory have been used (QCISD and QCISD(T)), which show several dramatic failings. Equilibrium electrical properties (u, ax, and axx) and basic spectroscopic properties (re, we. De, and infrared intensity (I)) have been computed. Basis set and electron correlation effects are analyzed in order to arrive at accurate values of the dipole moment and polarizability, which are not known experimentally. For the dipole moment, we obtain a value of 6.25 D, with an uncertainty of about 0.1 D. For ax and axx, we suggest respective values of 32 and 36 atomic units (au) and error bars of about 1 and 2 au with extended basis sets, the spectroscopic properties re, we, and De are reproduced to high accuracy, which is the first time this has been achieved for this species by ob initlo methods At the highest calculation levels, I is predicted to be very smalL Although I has not been measured, some support for this prediction comes from a recent infrared study of BeO-rare gas complexes The CCII methods are shown to be much more sensitive to basis set, and even with large basis sets yield values of ax and I which differ from CC results by an order of magnitude and three orders of magnitude, respectively. (AN).