short communications
Debye–Waller factors of five h.c.p. elements (Ti, Zr, Ru, Tm, Hf) have been determined from X-ray diffraction intensities. Within the limits of experimental errors, the Debye–Waller factors associated with the two principal directions are equal. The Debye temperatures (θM) have been evaluated. The energy of formation of vacancies (Ef) has been estimated from a semi-empirical relation between Ef and θ.