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Unformatted text preview: I The twobody term consists of three term as follows: U 2 = H ij r η ij + Z i Z j r 1 2 ( α i Z 2 j + α j Z 2 i ) r 4 exp [ r / r 4 s ] (4) I The terms are: (1) Steric repulsion due to ionic sizes (2) Coulomb interactions to take into account charge transfer (3) Chargedipole interaction due to electronic polarizabilities I Above, H ij and η ij are the strengths and exponents of the steric repulsion, Z i and α i represent the effective charge and electronic polarizability of the i th ion, respectively I For A 4 + and X 2 the effective charges are + 4 Q and 2 Q , respectively, where Q is the unit of charge transfer I The exponential screening term in the chargedipole interaction provides a reasonable cutoff for the ∝ r 4 interaction I The value of the decay length r 4 s is taken to be a few Å so that the magnitude of the chargedipole potential is reduced to a few percent of the term without the exponential I Although there are six threebody terms in the interaction potential or AX 2type systems, the two most important terms involve...
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 Winter '12
 Kotakoski
 Atom, Electric charge, charge transfer, Hij, Watanabe, Zi Zj

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