Accurate Calculation of the Dissociation Energy of the Highly Anharmonic System ClHCl-

摘要

Accurate bond dissociation energies (D-0) are reported for different isotopologues of the highly anharmonic system ClHCl-. The mass-independent equilibrium dissociation energy De was obtained by a composite method with frozen-core (fc) CCSD(T) as the basic contribution. Basis sets as large as aug-cc-pV8(+d)Z were employed, and extrapolation to the complete basis set (CBS) limit was carried out. Explicitly correlated calculations with the CCSD(T)-F12b method were also performed to support the conventionally calculated values. Core-core and core-valence correlation, scalar relativity, and higher-order correlation were considered as well. Two mass-dependent contributions, namely, the diagonal Born-Oppenheimer correction and the difference in zero-point energies between the complex and the HCl fragment, were then added in order to arrive at precise D0 values. Results for (ClHCl-)-Cl-35-Cl-35 and (ClDCl-)-Cl-35-Cl-35 are 23.81 and 23.63 kcal/mol, respectively, with estimated uncertainties of 0.05 kcal/mol. In contrast to FHF- (Stein , C. ; Oswald , R. ; Sebald , P. ; Botschwina , P. ; Stoll , H. , Peterson , K. A. Mol. Phys. 2013 , 111 , 2647-2652 ), the D-0 values of the bichloride species are larger than their De counterparts, which is an unusual situation in hydrogen-bonded systems.