The new 5-site ab initio intermolecular interaction potentials of dimer CO-CO were constructed from quantum mechanics using method CCSD(T) with Dunning's correlationconsistent basis sets aug-cc-pVmZ (m = 2, 3) [7]; ab initio energies were extrapolated to the complete basis set limit aug-cc-pV23Z. The ab initio intermolecular energies were corrected for the basis set superposition error (BSSE) with the counterpoise scheme [8]. | Journal of Chemistry, Vol. 47 (4), P. 506 - 510, 2009 INTERACTION SECOND VIRIAL COEFFICIENTS OF DIMER CO-CO FROM NEW AB INITIO POTENTIAL ENERGY SURFACE Received 2 May 2008 PHAM VAN TAT Department of Chemistry, University of Dalat abstract The new 5-site ab initio intermolecular interaction potentials of dimer CO-CO were constructed from quantum mechanics using method CCSD(T) with Dunning's correlationconsistent basis sets aug-cc-pVmZ (m = 2, 3) [7]; ab initio energies were extrapolated to the complete basis set limit aug-cc-pV23Z. The ab initio intermolecular energies were corrected for the basis set superposition error (BSSE) with the counterpoise scheme [8]. The interaction second virial coefficients of dimer CO-CO resulting from the 5-site ab initio analytical potential functions obtained by integration; first-order corrections for quantum effects were included too. The results agree well with experimental data. Keywords: Second virial coefficients, 5-site ab initio potentials. I - Introduction The knowledge of thermodynamic properties of the pure substance CO-CO is important for practical applications. It is also necessary for its safe use. Computer simulations have become indispensable tools for studying pure fluids and fluid mixtures and understand macroscopic phenomena. One of the first attempts Nasrabad and Deiters predicted phase high-pressure vapour - liquid phase equilibria of noble-gas mixtures [1, 2, 4] from the global simulations using the intermolecular potentials. Other mixed-dimer pair potentials for noble gases were published by Lãpez Cacheiro et al. [3], but not used for phase equilibria prediction, yet. This work presents quantum mechanical calculations at a sufficiently high level of approximation to obtain pair potential data of carbon monoxide using the high level of theory CCSD(T) with Dunning's correlation-consistent basis sets aug-cc-pVmZ (m = 2, 3) [7]; the complete basis set limit aug-cc-pV23Z is obtained 506 by ab initio .
