6533b820fe1ef96bd12799de

RESEARCH PRODUCT

A theoretical study of the collinear reaction F+H2→HF+H using multiconfigurational second-order perturbation theory (CASPT2)

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Abstract The second-order perturbation method (CASPT2) with a single state multiconfigurational reference function generated in complete active self-consistent field (CASSCF) calculations has been used to compute the collinear barrier height, saddle point geometry, and exothermicity of the reaction F+H 2 →HF+H. Comparison with full configuration (FCI) calculations with small basis sets shows that the CASPT2 method is capable of reproducing accurately the exact benchmark results correlating seven electrons. Large atomic natural orbital basis sets are used at the seven- and nine-electron level of correlation. With the largest ANO basis set used, F[7s6p5d4f2g]/H[6s5p4d2f], the computed nine-electron barrier height, 2.47 kcal/mol, is about 0.5 kcal/mol higher than results obtained using MRCI+Q and CCSD(T) methods employing basis sets of similar quality. The nine-electron exothermicity obtained with this basis set is 31.25 kcal/mol, about 0.5 kcal/mol below the experimental value.