An analysis of electronic polarizabilities, interionic potentials, and equilibrium geometries for 20 alkali–halide dimers such as Na2Cl2 is presented. The electronic polarizabilities of ions in dimers have been calculated by taking account of the electrostatic potential due to neighboring ions within the Seitz–Ruffa energy level analysis. The polarizabilities thus obtained for dimers are then used to evaluate the magnitudes of polarization energies and van der Waals dipole–dipole energies. For describing the overlap repulsive potential we have adopted two forms: (i) the revised version of the Born–Mayer potential and (ii) the Harrison form for the overlap repulsive energy. These potentials have been used to obtain the binding energies of monomers as well as dimers, spectroscopic constants of monomers, equilibrium geometries of dimers, and dimerization energies. The results have been discussed and compared with available experimental data.

An analysis of crystal binding and structural phase transition is presented using an analytical potential form for the overlap repulsive energy derived by Harrison from quantum mechanical considerations. The potential model is applied to calculate the cohesive energies, bulk modulus, and its pressure derivative for fifteen alkaline-earth chalcogenides and fourteen alkali chalcogenides. Calculated values of bulk modulus are found to exhibit empirical correlationship with unit cell volume. The problem of relative stability and structural phase transition is also investigated for alkaline-earth chalcogenides. Values of transition pressure are obtained and found to present good agreement with experimental data.Mit einer analytischen von Harrison aus quantenmechanischen Betrachtungen abgeleiteten Potentialform wird eine Analyse der Kristallbindung und der strukturellen Phaseniibergiinge durchgefuhrt. Das Potentialmodell wird zur Berechnung der Kohiisionsenergie, des Elastizitiitsmoduls und seinen Druckableitnngen von funfzehn Erdalkalichalkogeniden und vierzehn Alkalichalkogeniden benutzt. Es wird gefunden, da13 die berechneten Werte des Elastizitiitsmoduls eine empirische Korrelation mit dem Volumen der Einheitszelle aufweisen. Das Problem der relativen Stabilitiit und strukturellen Phasenubergiinge wird auch fur Erdalkalichalkogenide untersucht. Werte des Ubergangsdruckes werden erhalten und gefunden, da13 sie gut mit experimentellen Werten ubereinstimmen.

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Aromatic systems like phenol, diphenol, cyano benzene, chloro benzene, aniline etc shows effective π-π stacking interactions, long range van der Waals forces; ion-π interactions etc. and these forces of interactions play an crucial role in the stability of stacked π-dimeric system. On the other hand, substituents and conformational change in the stacked dimmers of aromatic system may also change the stability of different stacked dimers. In this current study, stacked phenolic dimmers (both phenol and diphenol) have been taken for investigation of the stacking π-π interaction. But, the stacking interactions are also greatly affected by the conformational change with internal rotation (i.e. dihedral angle, φ) between the stacked dimers. It is generally accepted that larger basis sets are required for the highly accurate calculation of interaction energies for any stacked aromatic models. But, it has recently been reported that M062X/6-311++G(d,p) basis set is effectively better than that of B3LYP/6-311++G(d,p) for determining the interaction energies for any kind of long range interaction in aromatic systems. Therefore, all the calculations were carried out by using M062X/6-311++G(d,p) basis set. However, in most of the cases the calculated π-π stacking interaction energies show almost same result for both DFT and ab initio methods.

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