Vibrational calculations for the H2O … CO complex

An accurate full-dimensional permutationally invariant potential energy surface for the interaction between H2O and CO

The first full-dimensional accurate potential energy surface was developed for the CO + H₂O system based onca.102 000 points calculated at the CCSD(T)-F12a/AVTZ level using a permutation invariant polynomial-neural network (PIP-NN) method.

The water–carbon monoxide dimer: new infrared spectra, ab initio rovibrational energy level calculations, and an interesting in-termolecular mode

Bound state rovibrational energy level calculations using a high-level intermolecular potential surface are reported for H₂O–CO and D₂O–CO.

Interaction of H2O with CO: potential energy surface, bound states and scattering calculations

We present the first scattering calculations for the H₂O–CO system based on a high accuracy potential energy surface.

VUV photochemistry of the H2O⋯CO complex in noble-gas matrices: formation of the OH⋯CO complex and the HOCO radical

VUV photolysis of the H₂O⋯CO complexes leads to the formation of the OH⋯CO radical–molecule complexes and trans-HOCO radicals.

Encapsulation kinetics and dynamics of carbon monoxide in clathrate hydrate

Carbon monoxide clathrate hydrate is a potentially important constituent in the solar system. In contrast to the well-established relation between the size of gaseous molecule and hydrate structure, previous work showed that carbon monoxide molecules preferentially form structure-I rather than structure-II gas hydrate. Resolving this discrepancy is fundamentally important to understanding clathrate formation, structure stabilization and the role the dipole moment/molecular polarizability plays in these processes. Here we report the synthesis of structure-II carbon monoxide hydrate under moderate high-pressure/low-temperature conditions. We demonstrate that the relative stability between structure-I and structure-II hydrates is primarily determined by kinetically controlled cage filling and associated binding energies. Within hexakaidecahedral cage, molecular dynamic simulations of density distributions reveal eight low-energy wells forming a cubic geometry in favour of the occupancy of carbon monoxide molecules, suggesting that the carbon monoxide–water and carbon monoxide–carbon monoxide interactions with adjacent cages provide a significant source of stability for the structure-II clathrate framework.

Carbon monoxide clathrate hydrate has been widely studied and although the structure-II gas hydrate is predicted to be thermodynamically favourable, it is the structure-I hydrate that has been observed. Here, the authors synthesize the structure-II carbon monoxide hydrate and probe its structure and formation.

From strong van der Waals complexes to hydrogen bonding: From CO⋯H2O to CS⋯H2O and SiO⋯H2O complexes

Structures and interaction energies of complexes valence isoelectronic to the important CO⋯H(2)O complex, namely SiO⋯H(2)O and CS⋯H(2)O, have been studied for the first time using high-level ab initio methods. Although CO, SiO, and CS are valence isoelectronic, the structures of their complexes with water differ significantly, owing partially to their widely varied dipole moments. The predicted dissociation energies D(0) are 1.8 (CO⋯H(2)O), 2.7 (CS⋯H(2)O), and 4.9 (SiO⋯H(2)O) kcal∕mol. The implications of these results have been examined in light of the dipole moments of the separate moieties and current concepts of hydrogen bonding. It is hoped that the present results will spark additional interest in these complexes and in the general non-covalent paradigms they represent.

Localization and anharmonicity of the vibrational modes for GC Watson-Crick and Hoogsteen base pairs

We present an ab initio study of the vibrational properties of cytosine and guanine in the Watson-Crick and Hoogsteen base pair configurations. The results are obtained by using two different implementations of the DFT method. We assign the vibrational frequencies to cytosine or to guanine using the vibrational density of states. Next, we investigate the importance of anharmonic corrections for the vibrational modes. In particular, the unusual anharmonic effect of the H(+) vibration in the case of the Hoogsteen base pair configuration is discussed.

Intermolecular potential energy surface and second virial coefficients for the nonrigid water-CO dimer

A seven-dimensional potential energy surface is calculated for the interaction of water and carbon monoxide using second-order Moller-Plesset theory, coupled-cluster theory, and extrapolated intermolecular perturbation theory. The effects of stretching the CO molecule and bending the water molecule are included. The minimum energy structure of the water-CO dimer changes from an H-C hydrogen bond to an H-O hydrogen bond when the CO bond length increases by less than 10 pm from its equilibrium value. Second virial coefficients for the water-CO interaction are calculated for a wide range of temperatures and compared with the limited experimental data. Allowing the CO bond length and water bond angle to vary has little effect on the second virial coefficients.