Inter-ionic repulsive interactions

For ionic solids interacting with Coulomb pair potentials, similar calculations can be carried out. However, this is a rather complex matter because Coulomb, van der Waals attraction and Pauli repulsion should all be taken into account. In addition, there are uncertainties in the choice of suitable pair-potential equation (many inter-atomic potential equations, including Lennard-Iones were tried), and the calculated Gf results are highly dependent on the particular choice of pair-potential model. As an example, Gf = 212m) m 2 was calculated theoretically for the NaCl (100) crystal, which is near to the experimental value of Gf = 190 m) m 2 from extrapolation of the molten salt surface tension values, but far away from Gf = 300 mj m 2, which was found from crystal cleavage experiments. 

For our purpose, the most interesting result in Table 2 is the separation 3 to 8 eV spreading out each of the two a sets in each of the two molecules. It cannot be excluded that this effect contains a contribution from preferential interaction with C 2 s or C 2 p, or with S 3 s compared with S 3 p and the high-lying S 3 d. However, the main reason seems to be inter-ligand repulsion. The overlap integral (62) between two 2 s orbitals of adjacent fluorine ligands is close to 0.11 in CF4 and 0.05 in SF6 compatible with the observed / differences. It may be noted that the F—F distances in these two particular molecules are considerably shorter than twice the ionic radius of F in... 

The low adsorbance and the high thickness at low salt concentration are due to the electrostatic repulsion, i.e., the excluded volume between the charged groups of adsorbed polyions. As the ionic strength is increased, the intra- and inter-polyion interactions of adsorbed NaPSS chains diminish so that a larger adsorbance and smaller thickness should be obtained. 

Thus Dr. Burawoy s statement that our calculations are based on the assumption that the A—H bond is mainly ionic, appears to be erroneous. The hydrogen bond energy equation (3) (page 386 of my paper) is based on general considerations and is valid for the interaction of B both with the homopolar (A—X) and with the Ionic molecule (A X+) and elucidates the process of interaction of the polar molecule with an atom and the role played by hydrogen in the formation of inter- (end intra-) molecular bonds. Contrary to Burawoy s statement equation (3) certainly takes into account the repulsion, between H and B. 

A similar calculation can be done for ionic crystals. In this case the Coulomb interaction is taken into account, in addition to the van der Waals attraction and the Pauli repulsion. Although the van der Waals attraction contributes little to the three-dimensional lattice energy, its contribution to the surface energy is significant and typically 20-30%. The calculated surface energy depends sensitively on the particular choice of the inter-atomic potential. 

In the strongly-correlated limit, when the electron delocalization (i.e. the tpq terms) becomes smaller than the electron repulsion U, an appropriate description of the lowest states is provided by the neutral VB determinants only, i.e. those in which each carbon p bears one unpaired electron in its n atomic orbital (AO, hereafter labelled 5 ). The n electron systems behaves as a pure spin system, obeying a Heisenberg Hamiltonian [22,23]. The inter-atomic delocalization, i.e. the interaction between the neutral VB distributions and the ionic ones, results in an antiferromagnetic spin coupling on each bond. One of the below-discussed rules, known as the Ovchinnikov s mle [21], has been derived from this magnetic approach. Numerous works [24] have shown the relevance of magnetic descriptions... 

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