Nonspherical molecules, second

The term m = 0.74048 Vm°/Vm = 1/6 7rN0cJm/Vm> where Vm° is the close-packed volume, N0 is the Avogadro number, and Vm is the molar volume of the system. V° is a simple function of the temperature (T) (10) with a characteristic value V°° at T = 0 K. The last term in Equation 12 was introduced by Alder et al. (II). Dnm are 24 universal constants common for all substances whose radial and higher distribution functions are the same functions of u/kT and the reduced density p = V°/V. As shown by Chen and Kreglewski (10) and Simnick, Lin, and Chao (12), Equation 12 is the most accurate known equation with four characteristic constants a, V°° (V° at T = 0 K), u°/k, and rj/k (see Equations 13 and 14). They also have shown (10) that in order to obtain agreement with second virial coefficient data of the gas and the internal energy or the enthalpy of the liquid, it is necessary to assume that u(r) is a function of T as required by the theory of noncentral forces between nonspherical molecules (13)... 

Theoretically, the second and the third virial coefficient can be calculated from models for the potential functions and with the help of the statistical mechanics. However, this procedure is rarely used in practical applications and tends to be extremely complex and even approximate for nonspherical molecules. 

J. Corner, The second virial coefficient of a gas of nonspherical molecules, Proc. Roy. Soc. (London) A192, 275-292 (194). 

It is obvious, that the presence of the property Loc and the lack of the property Con are necessary for superfluidity. But there is one more obvious and important condition for superfluidity molecules of second liquid must have the central symmetry ideally, they must be spherical (as it takes place for helium). For this reason, the most perspective for superfluidity in the bulk phase are elements of the eighth group (neon, argon and so on), whose molecules (atoms) have the central symmetry. Nonspherical molecules (for instance, the lineal molecules CO2 O - C - O) cannot bring superfluidity, as they are a cause of viscosity. 

In Section II of this article formulas which will be used later are derived in an elementary way in Section III the convex cores of molecules are determined. Diffusion of heavy molecules is discussed in Section IV with use of the rigid convex model of molecules. The intermolecular potentials for nonspherical molecules are calculated in Section V from the second virial coefficients their applications to crystalline states are given in Section VI. Section VII treats the role of the electric multipole interactions for convex or quasi-convex molecules in crystals. 

The first term on the right hand side of Equation (4.35), accounts for simple molecules, while the second term, is a correction factor for the nonsphericity of a species. Both and depend only on Tr and P. ... 

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