Van der Waals coefficient

Thakkar A J 1984 Bounding and estimation of van der Waals coefficients J. Chem. Phys. 81 1919... 

Tang K T 1969 Dynamic polarizabilities and van der Waals coefficients Phys. Rev. 177 108... 

W. Wang, J. Wang, and P. A. Kollman, What determines the van der Waals coefficient P... 

The study of behavior of many-electron systems such as atoms, molecules, and solids under the action of time-dependent (TD) external fields, which includes interaction with radiation, has been an important area of research. In the linear response regime, where one considers the external held to cause a small perturbation to the initial ground state of the system, one can obtain many important physical quantities such as polarizabilities, dielectric functions, excitation energies, photoabsorption spectra, van der Waals coefficients, etc. In many situations, for example, in the case of interaction of many-electron systems with strong laser held, however, it is necessary to go beyond linear response for investigation of the properties. Since a full theoretical description based on accurate solution of TD Schrodinger equation is not yet within the reach of computational capabilities, new methods which can efficiently handle the TD many-electron correlations need to be explored, and time-dependent density functional theory (TDDFT) is one such valuable approach. 

The van der Waals coefficients a and b are determined experimentally for each gas. For CO2 they are a=3.610 atmL2mol-2 and >=0.0429 Lmol1. The approximation is not perfect and negative volumes are computed at certain ranges of pressure and temperature. These values are replaced by zero. 

The coefficients a and b are two-dimensional analogs of the three-dimensional van der Waals coefficients. 

Table 6.1 Contributions of the Keesom, Debye, and London potential energy to the total van der Waals interaction between similar molecules as calculated with Eqs. (6.6), (6.8), and (6.9) using Ctotal = Corient + Cind + Cdisp- They are given in units of 10-79 Jm6. For comparison, the van der Waals coefficient Cexp as derived from the van der Waals equation of state for a gas (P + a/V fj (Vm — b) = RT is tabulated. From the experimentally determined constants a and b the van der Waals coefficient can be calculated with Cexp = 9ab/ (47T21V ) [109] assuming that at very short range the molecules behave like hard core particles. Dipole moments /u, polarizabilities a, and the ionization energies ho of isolated molecules are also listed.

Several workers 10- 11 have proposed revised van der Waals coefficients in alkali halides which eliminate the need for employing high van der Waals terms in the study... 

In order to employ the Born treatment to explain the transformations of CsCl + CsBr solid solutions, we have used the revised van der Waals coefficients of CsBr proposed by Hajj.10 The repulsive parameters of CsBr can be evaluated as follows (i) In the expression for the lattice energy (eqn. (3)) we have assumed that p2 = apx as proposed by Rao and Rao.3 (ii) We calculate (8 >t + 662)CsBr by substituting the value of p, obtained from the compressibility relations.2... 

Before presenting the results which have been obtained for sodium chloride it is necessary to indicate the sources of the data used for this salt. Van der Waals coefficients were taken from a tabulation by Mayer (11) and electronic polarizabilities of the ions at zero frequency from the work of Tessman, Kahn, and Shockley (13). A value of 4.802 X 10-10 e.s.u. was used for the charge of the electron and the repulsive parameters by and p were taken from recent publications by Cubicciotti (5, 6). A value of a — 2.794 A. was computed for the nearest... 

Pressure (Pt), Van Der Waals Coefficients a and b, Second Virial Coefficients B(T) at 273 K, and Joule-Thomson Inversion Temperature 7 (at 1 atm) for Several Elements and Compounds [1-3] ... 

The atomicity of phosphorus vapour under the critical conditions may be calculated from the van der Waals coefficient b, which represents the actual volume occupied by the molecules and is given by the equation3... 

The triplet curves for the Group lA diatomics were synthesized from molecular beam scattering data. The values of 0 were obtained from the glory scattering experiments of Helbing and Rothe (40) on alkali-alkali pairs interacting in the state. We have used their values for O which were obtained with the constraint of the van der Waals coefficient (Set A, Ref. 40). The values of the well depth were taken from the spin exchange experiments of Pritchard et al. (41). These authors found the well... 

Interaction parameter in Flory-Huggins treatment of polymer mixtures after normalization on a per monomer basis this becomes Xay also susceptibilities in discussion of density functional theories. Applied external field acting on species a in conformation X". Applied external field as a function of position acting on species a. Contribution of attractive interactions to the second virial coefficient for species pair ay also van der Waals coefficient. 

Monte Carlo calculations for structure 1 and 2, in order to obtain the two free energy curves. MM interaction potentials of the type shown in eq.(119) are used here. The solute parameters (atomic charges and van der Waals coefficients) are drawn from SCF calculation on the trimer 1 and 2, as well as on other small solvation clusters ... 

Rijks W and Wormer P E S 1990 Erratum correlated van der Waals coefficients. II. Dimers consisting of... 

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