Vekhov Y. Kinetics of bcc-hcp transition and thermodynamic properties of solid helium-4

The thesis combines results of kinetic and thermodynamic studies of solid helium near bcc-hcp phase transition. The experimental data on kinetics of bcc-hcp phase transition in solid 4He are obtained for the first time by precise pressure measurements. The kinetics of pressure and temperature changing at the melting curve indicates remelting during bcc-hcp transition and far from the melting curve - martensitic transformation. The data on nucleation kinetics under bcc-hcp transition are obtained for the first time. The line of attainable supercooling has been discovered and the interphase surface tension coefficient has been estimated. It has been shown for the first time that thermodynamic behavior of solid 3He and 4He are well described by combination of phonon Debye model and Hetherington's model for wide-band vacancies. Simple relations have been proposed for Debye temperature and vacancy activation energy depending on molar volume. It allows to describe specific heat jump under bcc-hcp transition in 4He.