LARGE-SCALE COUPLED CLUSTER CALCULATIONS FOR THE TWO RENNER-TELLER COMPONENTS OF HCCO

Abstract

CCSD(T) calculations with basis sets of up to 282 contracted Gaussian-type orbitals have been carried out in order to establish accurate equilibrium structures for the trans-bent lower $(^{2}A^{\prime\prime})$ and linear upper $(^{2} A^{\prime})$ Renner-Teller components of HCCO : a): $^{2} A^{\prime\prime}: r_{e} (CH)= 1.0709$ {\AA}, $R_{le} (CC)=1.2975$ {\AA}, $R_{2e} (CO)= 1.1710$ {\AA}, $\alpha_{e} (HCC)=134.1^{\circ}$ and $\beta_{e} (CCO)=169.3^{\circ} b) ^{2} A^{\prime} (^{2}\Pi): r_{e}=1.0604$ {\AA}, $R_{le}=1.2600$ {\AA}, and $R_{2e}=1.1834$ {\AA}. The barrier height to linearity of the $^{2}A^{\prime\prime}$ component is predicted to be $637 cm ^{-1}$.