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首页> 外文期刊>Zeitschrift fur Naturforschung. A, A journal of physical sciences >NQR Investigation of Anion Dynamics in Rb_2Zn(Cl_(1-x)Br_x)_4
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NQR Investigation of Anion Dynamics in Rb_2Zn(Cl_(1-x)Br_x)_4

机译：Rb_2Zn（Cl_（1-x）Br_x）_4阴离子动力学的NQR研究

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摘要

The structural stability of Rb_2Zn(Cl_(1-x)Br_x)_4 (x = 1% and 3%) is investigated using the ~(35)Cl quadrupole resonance frequency and spin lattice relaxation time (T_(1Q)) in the paraelectric (PE) phase. The PE to incommensurate (IC) phase transition temperature T_Ⅰ observed at 302 K in the pure compound, is lowered to 300 K for x = 1% and to 293 K for x = 3%. These effects are smaller than in the earlier reported case of 3% Cs substitution in Rb_2ZnCl_4, which reduces T_Ⅰ by 25 K. While bigger cation substitution affects only the barrier for anion dynamics about directions perpendicular to the a-axis (direction of low temperature IC modulation wave), bigger anion substitution is found to affect the barrier for anion dynamics about the a-axis as well. The present study also indicates that the cusp like dip in T_(1Q) observed while approaching T_Ⅰ from above (characterizing the soft mode condensation associated with the structural phase transition) is essentially unaffected by anion impurity substitution, in contrast to the case where bigger cation substitution tends to smear the transitional effects. These results seem to suggest the dominant role played by cations in stabilizing the PE phase of these A_2BX_4 systems, in comparison to anions.
机译：在顺电中使用〜（35）Cl四极共振频率和自旋晶格弛豫时间（T_（1Q））研究Rb_2Zn（Cl_（1-x）Br_x）_4（x = 1％和3％）的结构稳定性（PE）阶段。在纯化合物中，在302 K下观察到的PE到不相称（IC）相变温度T_Ⅰ，对于x = 1％，降低到300 K，对于x = 3％，降低到293K。这些影响小于先前报道的Rb_2ZnCl_4中3％Cs取代的情况，后者将T_Ⅰ降低了25K。而更大的阳离子取代仅影响阴离子在垂直于a轴方向（低温IC方向）上的动力学势垒。调制波），发现更大的阴离子取代基也会影响阴离子围绕a轴的动力学势垒。本研究还表明，从上方接近T_Ⅰ时观察到的T_（1Q）尖点状下降（表征与结构相变有关的软模式缩合）基本上不受阴离子杂质取代的影响，与阳离子较大的情况相反替代倾向于涂抹过渡效果。这些结果似乎表明，与阴离子相比，阳离子在稳定这些A_2BX_4系统的PE相中起主要作用。

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