Vibrational dependence of the anisotropic intermolecular potential of argon-hydrogen chloride

2003

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Semiempirical potential energy surfaces for the lowest three electronic states of the open-shell complex Br-HF are constructed, based on existing empirical potentials for Kr-HF and Kr-Ne and coupled-cluster electronic structure calculations for Br-Ne. Coupled cluster calculations are also described for He-F, Ne-F and Ar-F. Electrostatic interactions that arise from the quadrupole of the Br atom and the permanent multipoles of HF are also included in the Br-HF surfaces. The well depth of the lowest adiabatic surface is found to be 670 cm Ϫ1 at a linear equilibrium geometry. The results of helicity decoupled and full close-coupling calculations of the bound states of the complex are also described. The ground state, with total angular momentum projection quantum number ͉P͉ϭ3/2, is found 435 cm Ϫ1 below dissociation to Br ( 2 P 3/2 )ϩHF ( jϭ0). The lowest-frequency intermolecular bending and stretching vibrations are predicted around 145 and 211 cm Ϫ1 , respectively. Parity splittings are found to be extremely small for bound states with projection quantum number ͉P͉ϭ3/2. The relevance of the results to recently recorded spectra of Br-HF is discussed.

Section: Potential Energy Surfaces Including Spin-orbit Couplingmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Potential energy surfaces and bound states for the open-shell van der Waals cluster Br–HF

Meuwly

2003

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“…For Ar-HF 1 and Ar-HCl, 2 it was possible to extract empirical potentials with an explicit dependence on the mass-reduced quantum number ϭ(vϩ1/2)/ͱ HX . The experimental data available for Ne-HF and Ne-DF are not sufficient to do this reliably at present.…”

Section: B the Recommended Ne-hf Potentialmentioning

confidence: 99%

“…For prototype systems such as Ar-HF, 1 Ar-HCl, 2 He-CO, 3 Ar-CO 2 , 4 (HF) 2 , 5 and (HCl) 2 6 it has been possible to use extensive experimental information from the spectroscopy of Van der Waals complexes to develop accurate and reliable potential energy surfaces. In parallel with this, there have been substantial advances in electronic structure calculations: it is now possible to carry out ab initio calculations that give potentials approaching spectroscopic accuracy.…”

Section: Introductionmentioning

confidence: 99%

Morphing ab initio potentials: A systematic study of Ne–HF

Meuwly

1999

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145

139

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A procedure for ''morphing'' an ab initio potential energy surface to obtain agreement with experimental data is presented. The method involves scaling functions for both the energy and the intermolecular distance. In the present work, the scaling functions are parametrized and determined by least-squares fitting to the experimental data. The method is tested on the system Ne-HF, for which high-resolution infrared spectra are available. It is shown to work well even with relatively low-level ab initio calculations. Several basis sets are investigated at the CCSD͑T͒ correlation level, including various aug-cc-pVnZ basis sets and the specially-tailored Ne-HF basis set of ONeil et al.All give good results after morphing, but the changes needed to match experiment are much smaller for the ONeil basis set. The use of MP2 calculations is also investigated: again, the MP2 potential is quite satisfactory after morphing, but requires much more modification than the CCSD͑T͒ potential.

“…Highresolution spectra of van der Waals complexes have been used to determine accurate and reliable anisotropic pair potentials for systems such as Ar-HF 1 and Ar-HCl. 2 These potentials have been shown to perform well for newly measured properties such as the parameters of additional bands in the spectra of the van der Waals complexes, 3,4 inelastic cross sections, 5 and infrared pressure broadening coefficients. 6 The potentials have also been used to calculate the spectra of van der Waals trimers such as Ar 2 -HF and Ar 2 -HCl.…”

Section: Introductionmentioning

confidence: 98%

Nonadditive intermolecular forces in Arn–HF van der Waals clusters: Effects on the HF vibrational frequency shift

Liu

Moskowitz

et al. 1999

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The effects of nonadditive forces on Arn–HF van der Waals clusters are investigated for n=2, 3, 4, and 12. The pair potentials operating in these systems are accurately known. Earlier models of nonadditive forces in Ar2–HF, including nonadditive dispersion, induction, and overlap distortion, are generalized to handle clusters of arbitrary size. Calculations of vibrational frequency shifts (redshifts) are then performed and compared with experiment. The geometries of the clusters are first optimized by simulated annealing; the Arn cage is then held fixed, and the resulting five-dimensional Schrödinger equation is solved for the hindered rotational and translational motion of the HF molecule in the field of the Ar atoms. The nonadditive potentials are found to account remarkably well for the observed frequency shifts.