Knowledge Bank

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 $(2A\prime \prime )$ and linear upper $(2A\prime )$ Renner-Teller components of HCCO : a): $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}A\prime \prime :re(CH)=1.0709$ {\AA}, $Rle(CC)=1.2975$ {\AA}, $R2e(CO)=1.1710$ {\AA}, $\alpha e(HCC)=134.1\circ$ and $\beta e(CCO)=169.3\circ b)2A\prime (2\Pi ):re=1.0604$ {\AA}, $Rle=1.2600$ {\AA}, and $R2e=1.1834$ {\AA}. The barrier height to linearity of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}A\prime \prime$ component is predicted to be $637cm-1$.