Spectra of Ar–CO2 from ab initio potential energy surfaces

Self Cite

170

199

A new ab initio pair potential for water was generated by fitting 2510 interaction energies computed by the use of symmetry-adapted perturbation theory ͑SAPT͒. The new site-site functional form, named SAPT-5s, is simple enough to be applied in molecular simulations of condensed phases and at the same time reproduces the computed points with accuracy exceeding that of the elaborate SAPT-pp functional form used earlier ͓J. Chem. Phys. 107, 4207 ͑1997͔͒. SAPT-5s has been shown to quantitatively predict the water dimer spectra, see the following paper ͑paper II͒. It also gives the second virial coefficient in excellent agreement with experiment. Features of the water dimer potential energy surface have been analyzed using SAPT-5s. Average values of powers of the intermolecular separation-obtained from the ground-state rovibrational wave function computed in the SAPT-5s potential-have been combined with measured values to obtain a new empirical estimate of the equilibrium O-O separation equal to 5.50Ϯ0.01 bohr, significantly shorter than the previously accepted value. The residual errors in the SAPT-5s potential have been estimated by comparison to recent large-scale extrapolated ab initio calculations for water dimer. This estimatetogether with the dissociation energy D 0 computed from SAPT-5s-leads to a new prediction of the limit value of D 0 equal to 1165Ϯ54 cm Ϫ1 , close to but significantly more accurate than the best empirical value.

Section: ͑5͒mentioning

confidence: 93%

Water pair potential of near spectroscopic accuracy. I. Analysis of potential surface and virial coefficients

Mas

Bukowski

Szalewicz

et al. 2000

Self Cite

170

199

“…For vibrational ground state of CO 2 , these parameters are directly taken from Misquitta and co-workers. 18 Since the leading long range parameters C l 6 are dominated by dispersion, these terms for the excited state could be scaled by the vibrational averaged polarizability, 23…”

Section: A Potential Energy Surfacementioning

confidence: 99%

“…10,11 Extensive theoretical studies have been carried out by several groups to understand the experimental observations of van der Waals complexes formed by Ar and CO 2 . Due to the importance of the Ar−CO 2 interaction potential in modeling the structural and dynamic properties of such complexes, there have been a number of empirical 3,12,13 and semiempirical [14][15][16] dimer PESs fitted to the experimental data, as well as several ab initio [17][18][19] PESs with different approaches. Based on a few of the reported PESs, Severson 20 a) Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Finite temperature path integral Monte Carlo simulations of structural and dynamical properties of ArN−CO2 clusters

Wang¹,

Xie²

2012

We report finite temperature quantum mechanical simulations of structural and dynamical properties of Ar(N)-CO(2) clusters using a path integral Monte Carlo algorithm. The simulations are based on a newly developed analytical Ar-CO(2) interaction potential obtained by fitting ab initio results to an anisotropic two-dimensional Morse/Long-range function. The calculated distributions of argon atoms around the CO(2) molecule in Ar(N)-CO(2) clusters with different sizes are consistent to the previous studies of the configurations of the clusters. A first-order perturbation theory is used to quantitatively predict the CO(2) vibrational frequency shift in different clusters. The first-solvation shell is completed at N = 17. Interestingly, our simulations for larger Ar(N)-CO(2) clusters showed several different structures of the argon shell around the doped CO(2) molecule. The observed two distinct peaks (2338.8 and 2344.5 cm(-1)) in the υ(3) band of CO(2) may be due to the different arrangements of argon atoms around the dopant molecule.

“…20 to be superior to other possible choices, in particular to the equilibrium geometry. The center of mass of the molecule is located 0.07259 Å from the middle N. For the single-point calculations for He-CO 2 , the C-O distance was taken as 1.162453 Å, 21 the average distance in the ground-state vibration of CO 2 .…”

Section: Monomer Geometry and Basis Setmentioning

confidence: 99%

Potential energy surface and rovibrational spectrum of He–N2O dimer

Chang

Akin-Ojo

Bukowski

et al. 2003

Self Cite

Nitrous oxide dimer: A new potential energy surface and rovibrational spectrum of the nonpolar isomer J. Chem. Phys. 133, 134304 (2010); 10.1063/1.3494542Rotational spectrum, potential energy surface, and bound states of the weakly bound complex He-N 2 O Ab initio potential-energy surface for the He ( 1 S)+ NO (X 2 Π) interaction and bound rovibrational states Symmetry-adapted perturbation theory ͑SAPT͒ calculations were performed to determine a two-dimensional potential for the interaction of the helium atom with the nitrous oxide molecule. For selected geometries, correlated supermolecular calculations were used to verify SAPT data. The ab initio interaction energies were fitted to an analytic function and rovibrational energy levels of He-N 2 O were computed on the resulting surface. Extensive comparisons were made with a literature ab initio He-CO 2 potential and rovibrational states in order to rationalize the counterintuitive observations concerning spectra of N 2 O and CO 2 in superfluid helium nanodroplets. We conjecture that the greater reduction of the N 2 O rotational constant than that of CO 2 is related to the greater potential depth in the former case and the resulting greater probability of attaching helium atoms. An additional factor could be that the secondary minimum on the O side of N 2 O is 30% deeper than the linear minima in the case of CO 2 . As a by-product of this work, accurate multipole moments of N 2 O have been computed. The quadrupole, octupole, and hexadecapole moments are significantly different from experimental values and are probably more accurate than the latter.