Difusão de calor e o pico central em transições de fase estruturais

AUTOR(ES)

Edson Sardella

DATA DE PUBLICAÇÃO

1985

RESUMO

The coupling between polarization and temperature fluctuations in ferro and antiferroelectric crystals which undergo structural phase transitions is studied through Mori s formalism. Using thermodynamic considerations, we choose as dynamical variables the Fourier components of the local polarization, of its first time derivative and of the local temperature (the latter defined in terms of the Fourier components of the local energy density). We discuss conservation laws for these variables and their relationship to microscopic quantities describing the lattice dynamics, namely, the phonon field and phonon momentum operators. We obtain an expression for dynamical structure factor which has the same shape as the one derived using Green?s functions. In the long-wavelength limit and far from the critical region the structure factor exhibits a Brillouin pair and a central peak, whereas close to the critical region the Brillouin pair vanishes and the central peak diverges

ASSUNTO(S)

ferroeletricidade polarização (eletricidade) dinamica de redes

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