Rk. Subramanian et al., CL-35 NUCLEAR-QUADRUPOLE RESONANCE STUDY OF ANION DYNAMICS IN THE PARAELECTRIC PHASES OF CS2ZNCL4 AND RB2ZNCL4, Journal of physics. Condensed matter, 6(1), 1994, pp. 137-146
The dynamics of the ZnCl4 anion in two compounds, one exhibiting a str
uctural transition to an incomensurate phase (Rb2ZnCl4) and another no
t having any structural transition at all (Cs2ZnCl4), are studied thro
ugh Cl-35 NQR frequency (nu) and relaxation time (T1Q) measurements as
a function of temperature T in their high-temperature (paraelectric)
phases. Estimates of the potential barriers hindering the reorientatio
nal motions of ZnCl4 anions along axes parallel and perpendicular to t
he a axis of the crystal structure are obtained from the T1Q data. The
se results are analysed in conjunction with a qualitative comparison o
f relative mean square amplitudes of such motions obtainable from freq
uency data, in order to investigate the differences in the dynamics an
d structure of the ZnCl4 anion. There seems to be correlation between
the dynamics of the anion in this phase and the possibility that the c
ompound may exhibit a structural instability at low temperatures in th
is family.