Ab Initio Potential Energy Surface and Vibration-Rotation Energy Levels of Beryllium Monohydroxide

The accurate potential energy surface of beryllium monohydroxide, BeOH, in its ground electronic state X(2)A' has been determined from ab initio calculations using the coupledcluster approach in conjunction with the correlation-consistent core-valence basis sets up to septuple-zeta quality. The higher-order electron correlation, scalar relativistic, and adiabatic effects were taken into account. The BeOH molecule was confirmed to be bent at equilibrium, with the BeOH angle of 141.2 degrees and the barrier to linearity of 129 cm(-1). The vibration-rotation energy levels of the BeOH and BeOD isotopologues were predicted using a variational approach and compared with recent experimental data. The results can be useful in a further analysis of high-resolution vibration-rotation spectra of these interesting species. (C) 2016 Wiley Periodicals, Inc.