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Journal ArticleDOI

A simplified representation of intermolecular potential energy

15 Oct 1973-Chemical Physics Letters (North-Holland)-Vol. 22, Iss: 3, pp 443-446
TL;DR: In this article, a new simple function which is capable of representing the intermolecular pair potential energy of the inert gases is proposed, based on the traditional n -6 reciprocal power potential with the modification that n is regarded as a function of separation rather than as a constant.
About: This article is published in Chemical Physics Letters.The article was published on 1973-10-15. It has received 151 citations till now. The article focuses on the topics: Pair potential & Effective potential.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a simple and precise empirical intermolecular potential is proposed for helium, which is fitted to recent accurate intermediate temperature second virial coefficients and thermal conductivity data as well as high temperature viscosity values.
Abstract: A simple realistic and precise empirical intermolecular potential is proposed for helium. It possesses nearly the correct Hartree–Fock repulsion as well as the correct long range behavior. It was fitted to recent accurate intermediate temperature second virial coefficients and thermal conductivity data as well as high temperature viscosity values. It is able to predict second virial coefficients over an extended temperature range from 1.5 to 1475 K. Above 100 K it reproduces substantially all of the transport properties to within experimental error in a manner superior to all other potentials in existence. Below 100 K where the transport data are less reliable, it produces a good representation of the isotopic differences in the viscosity. It also predicts differential cross sections reasonably well. In spite of a few remaining discrepancies, when all the different macroscopic properties are considered, the potential produces the best representation of the helium interaction available at this time.

592 citations

Journal ArticleDOI
TL;DR: In this paper, a semi-empirical method for the prediction of intermolecular forces was proposed for systems with a small number of electrons and leads to the conclusion that those systems behave as the internal atomic correlation energy was almost independent from the interatomic distance.

459 citations

Journal ArticleDOI
TL;DR: Improved Lennard-Jones (ILJ) as discussed by the authors was proposed to eliminate the inadequacies at short and long-range of the LJ model and has been used for molecular dynamics simulations of both neutral and ionic systems.
Abstract: Scattering data, measured for rare gas-rare gas systems under high angular and energy resolution conditions, have been used to probe the reliability of a recently proposed interaction potential function, which involves only one additional parameter with respect to the venerable Lennard-Jones (LJ) model and is hence called Improved Lennard-Jones (ILJ). The ILJ potential eliminates most of the inadequacies at short- and long-range of the LJ model. Further reliability tests have been performed by comparing calculated vibrational spacings with experimental values and calculated interaction energies at short-range with those obtained from the inversion of gaseous transport properties. The analysis, extended also to systems involving ions, suggests that the ILJ potential model can be used to estimate the behavior of unknown systems and can help to assess the different role of the leading interaction components. Moreover, due to its simple formulation, the physically reliable ILJ model appears to be particularly useful for molecular dynamics simulations of both neutral and ionic systems.

259 citations

Journal ArticleDOI
TL;DR: In this article, the potential energy surfaces are represented by a simple analytical form written as a sum of atom-bond interaction contributions, for which a new potential model, [ n ( x ), m ], is proposed.

213 citations

Journal ArticleDOI
TL;DR: In this article, anisotropic potential energy surfaces were obtained by simultaneous least squares fitting to molecular beam spectra and rotational line broadening cross sections, with the potentials all very similar in shape and the absolute minimum at the linear rare gas-HCl geometry in each case.
Abstract: Anisotropic potential energy surfaces for Ne·HCl, Kr·HCl and Xe·HCl are obtained by simultaneous least squares fitting to molecular beam spectra and rotational line broadening cross sections. A revised potential surface for Ar·HCl is also presented. The potentials are all very similar in shape, with the absolute minimum at the linear rare gas—HCl geometry in each case. The absolute well depths and well depth anisotropies increase steadily as the size of the rare gas atom increases. The potentials should be reliable in the region of the absolute minimum and on the repulsive wall of the potential. The molecular beam spectra for Ne·HCl can be fitted only by a potential with a significant secondary minimum at the linear Ne·Cl-H geometry, but the existing data for the more anisotropic Ar, Kr and Xe systems are not sensitive to the presence of this potential feature. The potential surfaces for these systems have accordingly been constrained to have a similar secondary minimum near the linear rare gas-ClH geomet...

166 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the Axilrod-Teller three-body interaction was used to calculate the pair-potential functions of solid and gaseous argon and liquid argon.
Abstract: Thermodynamic properties of liquid argon are calculated by Monte Carlo and molecular dynamics techniques, using accurate pair-potential functions determined from the properties of solid and gaseous argon, together with the Axilrod-Teller three-body interaction. Satisfactory techniques for evaluating three-body contributions to thermodynamic properties without excessive requirements of computer time are described. Quantum corrections are included. Agreement with experiment is excellent: the best pair and triplet potentials give an excellent description of the properties of solid, gaseous and liquid argon.

515 citations

Journal ArticleDOI
TL;DR: In this article, high-resolution low-energy elastic differential cross sections have been measured for Ar-Ar over a wide angular range and Rainbow structure as well as symmetry oscillations at wide angels were resolved.
Abstract: High‐resolution low‐energy elastic differential cross sections have been measured for Ar–Ar over a wide angular range. Rainbow structure as well as symmetry oscillations at wide angels were resolved. These results are used to evaluate 16 different Ar–Ar potentials proposed previously and also to construct a new potential. Vibrational energy levels and the second virial coefficient calculated for the new potential are compared with experimental results.

284 citations

Journal ArticleDOI
TL;DR: In this paper, error bounds for the long-range attractive potential between pairs of atoms and molecules have been calculated by constructing oscillator strength distributions which reproduce known dynamic polarizabilities, oscillator strengths, and photoionization cross sections.
Abstract: Error bounds for the long‐range attractive potential between pairs of atoms and molecules have been calculated by constructing oscillator strength distributions which reproduce known dynamic polarizabilities, oscillator strengths, and photoionization cross sections. Results from the theory of moments are applied to construct these distributions so that they provide rigorous error bounds on the force constant. Approximate solutions to the moment equations which result are found by means of linear programming. Results obtained for rare‐gas interactions are found to be consistent with known values, with error bounds significantly tighter than those obtained from previous calculations. These same oscillator strength distributions are used to calculate error bounds on the dynamic polarizabilities for frequencies between those of the existing measurements and the first dipole‐allowed transition.

197 citations

Journal ArticleDOI
TL;DR: In this article, high-resolution differential cross sections for elastic scattering extending to wide scattering angles for He-He and Ne-Ne have been measured at two collision energies in the thermal range.
Abstract: High‐resolution differential cross sections for elastic scattering extending to wide scattering angles for He–He and Ne–Ne have been measured at two collision energies in the thermal range. The experiments were carried out by crossing two supersonic nozzle atom beams at right angles and detecting the atoms scattered in the plane of the beams with a rotatable electron‐bombardment mass‐filter universal detector. The results are analyzed to yield information on the interatomic potentials for these systems using a realistic and flexible potential function, and comparison is made with previously proposed potentials. For He2, a somewhat ``harder'' low‐energy repulsion than that of most such potentials is inferred, while for Ne2 the potential well depth found is ∼ 30 % larger than earlier estimates and in good agreement with a preliminary spectroscopic finding.

188 citations