A critical evaluation of Lennard–Jones and Stockmayer potential parameters and of some correlation methods

1977 ◽  
Vol 55 (16) ◽  
pp. 3007-3020 ◽  
Author(s):  
Frank M. Mourits ◽  
Frans H. A. Rummens
Keyword(s):  
Critical Evaluation ◽  
Viscosity Data ◽  
Priority Rules ◽  
Viscosity Measurements ◽  
Lennard Jones ◽  
Correlation Methods ◽  
Correlation Techniques ◽  
Parameter Values ◽  
Potential Parameters

Published values for the potential parameters σ and ε/k of the Lennard–Jones (12–6) and Stockmayer (12–6–3) potentials as based on viscosity measurements are reviewed, with particular reference to the problem of indeterminacy inherent to such calculations. A number of correlation techniques, calibrated on viscosity-based potential parameters, are critically reviewed; where possible, priority rules for the use of these correlations have been developed. In addition, several other criteria (i.e. not based on viscosity data) for the acceptance or rejection of σ and ε/k parameter values are also discussed. Upon application of the various criteria and priority rules it has been possible to give recommended σ and ε/k parameter values for 75 molecules.

scholarly journals The 7Be(p, ?)8B Cross Section at Low Energies

1980 ◽  
Vol 33 (2) ◽  
pp. 177 ◽  
Author(s):  
FC Barker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Solar Neutrinos ◽  
Model Calculations ◽  
Spectroscopic Factors ◽  
Low Energies ◽  
Standard Values ◽  
Experimental Values ◽  
Parameter Values ◽  
Potential Parameters

The nonresonant part of the 7Be(p, )I)8B cross section at low energies is recalculated by means of a direct-capture potential model, using parameter values determined by fitting 7Li(n, n)7Li and 7Li(n, )I)8Li data. Standard values of the potential parameters and spectroscopic factors give values of the 7Li(n,)I) cross section that are too large. Modified values that fit the thermal-neutron capture cross section predict 7Be(p,)I) cross sections that are much less than the experimental values. Also, shell model calculations predict resonant 7Be(p,)I) cross sections that are smaller than the experimental values. It is suggested that the accepted experimental values of the 7Be(p, )I) cross section may be too large, perhaps due partly to an overlarge accepted value for the 7Li(d, p)8Li cross section, which has been used for normalization purposes. A decrease in the 7Be(p,)I) cross section would reduce the calculated detection rate of solar neutrinos and lessen the discrepancy with the measured value.

scholarly journals Intermolecular potential parameters and combining rules determined from viscosity data

2010 ◽  
Vol 42 (12) ◽  
pp. 713-723 ◽  
Author(s):  
Lucas A. J. Bastien ◽  
Phillip N. Price ◽  
Nancy J. Brown
Keyword(s):  
Intermolecular Potential ◽  
Viscosity Data ◽  
Potential Parameters

The structure of the diatomic molecular solids

1974 ◽  
Vol 340 (1620) ◽  
pp. 57-80 ◽  
Keyword(s):  
Thermal Effects ◽  
Molecular Shape ◽  
Stable Structure ◽  
Crystallographic Structure ◽  
Molecular Solids ◽  
Quadrupole Moments ◽  
Lennard Jones ◽  
Parameter Values ◽  
Atom Potential ◽  
Great Simplicity

A simple model of the low temperature phases of the diatomic molecular solids is examined. The model consists of molecules, interacting via a Lennard-Jones atom-atom potential and quadrupole-quadrupole interactions. The internal energy of any crystallographic structure (excluding thermal effects) can then be given in terms of two dimensionless parameters, which describe the deviation of the molecular shape from a sphere and the relative importance of the quadrupole energy. The minimum energies and optimum molecular configurations in several structures are computed, for values of these dimensionless variables which span the values appropriate to the actual homonuclear diatomic molecular solids, H 2 , N 2 , O 2 , F 2 , Cl 2 , Br 2 and I 2 . Despite its great simplicity, the model is able to explain several features of these structures. These are (i) o -H 2 and N 2 have the optimum quadrupole structure, Pa3; (ii) β-O 2 is one of the optimum van der Waals’ structures, R3 ¯ m; (iii) the monoclinic α-F 2 structure is the most stable structure for parameter values very close to those appropriate to F 2 ; (iv) the ortho-rhombic Cmca structure (observed for Cl 2 , Br 2 and I 2 ) is the most stable structure for a large range of quadrupole moments which may be appropriate to these molecules. The model, is, of course, unable to take into account intermolecular bonding or spin-dependent interatomic forces. The former is important for the halogens and the latter for the (magnetic) oxygen molecule. The case of α-O 2 is treated in the following paper.

ANHARMONIC CONTRIBUTIONS TO THE BULK MODULUS AND CHARACTERISTIC TEMPERATURES OF NEON AND ARGON AT T = 0 °K

1967 ◽  
Vol 45 (9) ◽  
pp. 2995-2997 ◽  
Author(s):  
J. S. Brown ◽  
G. K. Horton
Keyword(s):  
Bulk Modulus ◽  
Excellent Agreement ◽  
Characteristic Temperature ◽  
Experimental Results ◽  
Debye Characteristic Temperature ◽  
Characteristic Temperatures ◽  
Lennard Jones ◽  
Anharmonic Potential ◽  
Potential Parameters

Anharmonic contributions to the bulk moduli of Ne and Ar are calculated for Lennard-Jones (m–6) potentials and compared with the experimental results at T = 0 °K. We consider direct anharmonic contributions to the bulk moduli and the anharmonic contributions via the use of Brown's (1966) anharmonic potential parameters. Excellent agreement is found with the experimental results of Peterson, Batchelder, and Simmons (1966) and Batchelder, Losee, and Simmons (1967).We also study the effect of the anharmonic parameters on the Debye characteristic temperature obtained from Cν. Improved agreement with the experimental results is found.

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