Intermolecular potential and second virial coefficient of the water-nitrogen complex

Abstract

The authors construct a rigid-body (five-dimensional) potential energy surface for the water-nitrogen complex using the systematic intermolecular potential extrapolation routine. The intermolecular potential is then extrapolated to the limit of a complete basis set. An analytic fit of this surface is obtained, and, using this, the global minimum energy is found. The minimum is located in an arrangement in which N2 is near the H atom of H2O, almost collinear with the OH bond. The best estimate of the binding energy is 441 cm-1 (1 cm-1 approximately 1.986 43x10(-23) J). The extrapolated potential is then used to calculate the second cross virial coefficient over a wide temperature range (100-3000 K). These calculated second virial coefficients are generally consistent with experimental data, but for the most part the former have smaller uncertainties.

Time‐dependent coupled‐cluster calculations of polarizabilities and dispersion energy coefficients

“…The numerical integration to obtain the dispersion energy coefficients for Li-Li is therefore based on tan −1 (10ω), so ω k = tan((2k − 1)π/(4N))/10 and Table 1 compares spherically averaged dispersion energy coefficients obtained with the TD-CCSD method using different basis sets. The basis sets denoted DZ, TZ, and QZ are the aug-cc-pVDZ, augcc-pVTZ, and aug-cc-pVQZ basis sets, respectively, 17,18 whereas the SPTZ and SPQZ basis sets are modified versions of these, 4,19 which are designed to improve the convergence of the higher dispersion energy coefficients by reducing the exponents of the polarization functions. The literature values quoted are obtained from scaled dipole oscillator strength distributions.…”

“…Relaxed orbitals give results which are formally correct to a higher order in the correlation operator than nonrelaxed orbitals, 26 and the advantage of using relaxed orbitals for frequency-independent properties, including the polarizability of CO, has been demonstrated by direct comparison between the two methods. 28 Additional calculations of dispersion coefficients using the CCSD method with nonrelaxed orbitals have been performed using the Dalton program 29 ; upper and lower bounds on the dispersion coefficients were obtained by fitting a [3,4] Padé approximant to the Cauchy moments 30 and the results are shown in Table 2 as "NR-CCSD". In general, the dispersion energy coefficients obtained from nonrelaxed orbitals appear to be larger, but there is not clear evidence in support of either relaxed or nonrelaxed orbitals.…”

“…The terms in eq. (1) can be multiplied by suitable damping functions f n (R), [1][2][3][4] which are 1 for large R and rapidly tend to zero as R decreases, to correct the divergence of the series.…”

A molecular beam scattering study of the weakly bound complexes of water and hydrogen sulphide with the main components of air

“…Maximum estimated uncertainty is 3% for ε, 1% for r m and 2% for the ε r m product. Results from semi-empirical correlations formulas [37,[40][41][42] (maximum estimated uncertainty 15% for ε and 5% for r m ) and ab initio calculations [21,22] are also reported for comparison.…”

“…Direct information coming from gas phase molecular beam scattering experiments, to our knowledge, is not available. Scattering data could be crucial also to test the validity of numerous theoretical calculations available on the intermolecular interactions [10,[17][18][19][20][21][22][23].…”