On localization of f-electrons in high temperature phases of early actinides

Abstract

It has been suggested by Vohra and Holzapfel that the f-electrons in early actinide elements become localized at high temperatures close to melting. Their conclusion is based on the unusually large thermal expansions of Np and Pu and their observation of the high temperature β-Np structure under pressure in trivalent 3d Sc, which does not have any f-electrons. We show that these have alternative explanations. Further, the atomic volumes of the high temperature bcc phases of U, Np and Pu are considerably lower than the ones calculated from band theory assuming localized f-electrons. We conclude that the f-electrons continue to be delocalized at high temperatures in U, Np and Pu except Pa.