Pitzer potential

K. S. Pitzer, Potential Energies for Rotation about Single Bonds . Discuss. Faradav Soc., 10,66-73 (1951). 

Here 1/ is the effective potential and a>i i is a nodeless pseudo-orbital that can be derived from Xi, in several different ways. For first-row atoms, Christiansen, Lee and Pitzer (1979) suggest... 

Kihara20 used a core model in which the Lennard-Jones potential is assumed to hold for the shortest distance between the molecular cores instead of molecular centers. By use of linear, tetrahedral, and other shapes of cores, various molecules can be approximated. Thomaes,41 Rowlinson,35 Hamann, McManamey, and Pearse,14 Atoji and Lipscomb,1 Pitzer,30 and Balescu,4 have used other models of attracting centers and other mathemtical methods, but obtain similar conclusions. The primary effect is to steepen the potential curve so that in terms of inverse powers of the inter-... 

In view of the complications of the intermolecular potential (as compared to the interatomic potential of the rare gas atoms) the comparisons for molecules in Tables II, III, and IV should be judged with caution. The apparent discrepancies from the theories for single atoms can be misleading. An example is the calculation for CH4 on the Slater-Kirkwood theory where Table IV shows the absurd value of 24 for the effective number of electrons. Pitzer and Catalano32 have applied the Slater-Kirkwood equation to the intermolecular potential of CH4 by addition of all the individual atom interactions and, with N = 4 for carbon and 1 for hydrogen, obtained agreement within 5 per cent for the London energy at the potential minimum. 

For a discussion of the calculation of corrections for junction potential, see G. N. Lewis, M. Randall, K. S. Pitzer and L. Brewer, Thermodynamics. Second Edition, McGraw-Hill, New York, 1961, pp. 362-364. 

We can find the reaction s equilibrium point from Equation 3.3 as soon as we know the form of the function representing chemical potential. The theory of ideal solutions (e.g., Pitzer and Brewer, 1961 Denbigh, 1971) holds that the chemical potential of a species can be calculated from the potential pg of the species in its pure form at the temperature and pressure of interest. According to this result, a species chemical potential is related to its standard potential by... 

W. Weltner, Jr., andK. S. Pitzer, Methyl alcohol The entropy, heat capacity and polymerization equilibria in the vapor, and potential barrier to internal rotation. J. Am. Chem. Soc. 73, 2606 2610 (1951). 

Since these early X-ray diffraction experiments, several other crystals have been subjected to analysis by X-ray and neutron diffraction and the F bond length has remained virtually unchanged. The location of the proton has been the point at issue. Early ir studies on KHF2 were interpreted as evidence for a double minimum potential well (Ketelaar, 1941 Glocker and Evans, 1942), but later studies questioned this (Pitzer and Westrum, 1947 Cote and Thompson, 1951 Newman and Badger, 1951) and led to a revision of earlier opinions (Ketelaar and Vedder, 1951). 

Infrared spectra. Early reports on the spectra of the difluoride salts divide into those which support (Pitzer and Westrum, 1947) or refute (Blinc, 1958) the idea of the anion having a single minimum potential energy well. This debate has rumbled on with Spinner remaining as the sole champion of the double minimum/low barrier profile, on the basis of the ir spectrum (Spinner, 1977, 1980a). A more contentious issue, however, is the assignment of the asymmetric stretching vibration, Vj. 

Pitzer and Gwinn have also provided tables to determine the thermodynamic contributions of hindered rotors (those having torsional barriers on the order of ksT) when such rotors are well described by the torsional potential... 

For restricted rotation, the thermodynamic functions can be calculated as a function of the height of the potential barrier Vo. Pitzer has assumed a potential of the form... 

The lattice enthalpy U at 298.20 K is obtainable by use of the Born—Haber cycle or from theoretical calculations, and q is generally known from experiment. Data used for the derivation of the heat of hydration of pairs of alkali and halide ions using the Born—Haber procedure to obtain lattice enthalpies are shown in Table 3. The various thermochemical values at 298.2° K [standard heat of formation of the crystalline alkali halides AHf°, heat of atomization of halogens D, heat of atomization of alkali metals L, enthalpies of solution (infinite dilution) of the crystalline alkali halides q] were taken from the compilations of Rossini et al. (28) and of Pitzer and Brewer (29), with the exception of values of AHf° for LiF and NaF and q for LiF (31, 32, 33). The ionization potentials of the alkali metal atoms I were taken from Moore (34) and the electron affinities of the halogen atoms E are the results of Berry and Reimann (35)4. 

W. M. Latimer, K. S. Pitzer, and C. M. Slansky, J. Ghent. Phys., 7,108 (1939). Free Energy of Hydration of Gaseous Ions and the Absolute Potential of the Normal Calomel Electrode. 

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