The CO molecule: the role of basis set and correlation treatment in the calculation of molecular properties

摘要: Abstract Although Hartree-Fock wave functions can provide a semi-quantitative description of the electronic structure molecules, accurate predictions cannot be made without explicit inclusion effects electron correlation. In correlated calculations, accuracy function is determined by two expansions: many-electron expansion in terms molecular orbitals that defines form and basis set used to expand one-electron orbitals. Thus, assess given (correlation method), it necessary examine dependence property on set. this work, systematic sequences correlation consistent sets ranging size from double- sextuple-zeta (cc- pVnZ ) have been employed together with several commonly methods, e.g., MPn ( n = 2 − 4), CCSD, CCSD(T), MRCI, calculate spectroscopic constants selected properties carbon monoxide molecule. The computed show excellent convergence toward complete (CBS) limit, intrinsic errors each method assessed compared. correlating ls-like core electrons also using sequence core-valence cc- pCVnZ CCSD(T) ACPF methods. A number other calculated for as set: dipole moment, quadrupole polarizability, first second hyperpolarizabilities. For these results aug-cc- are compared those obtained incorporating another shell diffuse functions, d-aug-cc- . case well-behaved CBS limit observed theoretical method. both properties, comparisons previous calculations available experimental data.