Vacancy-Impurity Nanoclusters in Solid Solutions $^3He - ^4He$
  The existence of vacancy--impurity clusters due to quantum properties of vacancies in phase separated solid solutions of 4He in 3He is analyzed and discussed. Additional mechanism called vacancy assisted nucleation is proposed. According to this assumption the vacancy-impurity clusters should have b.c.c. structure. 
Dimitar I. Pushkarov