Open AccessЭффекты фазового перехода, индуцированные давлением, в модельных сегнетоэластиках Hg-=SUB=-2-=/SUB=-Br-=SUB=-2-=/SUB=-
Author(s) -
Е.М. Рогинский,
А.С. Крылов,
Ю.Ф. Марков
Publication year - 2018
Publication title -
pisʹma v žurnal tehničeskoj fiziki
Language(s) - English
Resource type - Journals
eISSN - 1726-7471
pISSN - 0320-0116
DOI - 10.21883/pjtf.2018.17.46564.17346
Subject(s) - phonon , tetragonal crystal system , brillouin zone , degenerate energy levels , condensed matter physics , hydrostatic pressure , phase boundary , phase (matter) , spectral line , hydrostatic equilibrium , symmetry (geometry) , atmospheric temperature range , materials science , chemistry , physics , thermodynamics , mathematics , geometry , quantum mechanics
AbstractRaman spectra of model improper ferroelastics (Hg_2Br_2 crystals) have been analyzed in a wide range of hydrostatic pressures. The baric dependences of the phonon frequencies are obtained. The revealing and anomalous behavior of the soft mode, which is genetically related to the acoustic phonon (ТА_1) at the Brillouin zone boundary (point X ) of the tetragonal phase, are most interesting. The buildup of the second acoustic phonon (ТА_2) from the same point has also been found in the ferroelastic-phase spectra, and its baric behavior has been investigated. The splitting of doubly degenerate phonons of the E _g symmetry has been revealed at fairly high pressures and explained.