The change of lattice constanta due to order-disordering proceas in a superlattice is investigated by using the condition of minimum free energyin Bethe's theory. It is fonnd that tho interaction energy depends on the degree of order when the extornal presure is kept constant. The specific heat at constant pressure given by the theory is compared with experimeut. Another source of the variation of interactíon energy ia the change of atomic arrangements. This is also investigated from the viewpoint of Wang'8 formulation of the iree onergy in Bethe's approximation. The energy states of the configurationa 282p,2p2,182m2p,1s2p2,282p2,2p8 nhe atons fron H to F have been calculated. by the yariational method with gimple wave functions. Wherever' possible, thé enorgies are the corrected according to the method suggested by Stevenson. These caloulated or tha denon oe eee ne of stable negative ions of H and He in excitod staten is discussod. The electron affinity of Li atom is reestimated.
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