Correlation effects in metal ammonia systems
The recent structural and electrochemical measurements of the alkali metal-ammonia systems are reconciled in a model where the correlation energy leads to the formation of bound states. This is evident in the X-ray absorption of Rbx(NH3)1−x near the Rb K-edge as a white peak which appears only when the metal mole fraction is reduced below xc = 0.04. These transitions must be associated with the correlation effects which lead to the formation of sodium anions predicted by electrochemical measurements. If the anions act as impurity centers with a minus two valence change from the uniformly charged positive background, Friedel oscillations in the electron density must be taken into account in a statistical description of the system. The deviations of the activity coefficients from the usual Debye-Hückel expression are discussed.
KeywordsCharge Density Wave Spin Density Wave Excess Free Energy Knight Shift Boltzmann Statistic
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