在5K～300 K的温度范围内对六氯铅铵晶体进行了拉曼散射测量,该晶体在Tc＝78K发生从立方结构(O5k)至三方结构(C23i)的二级相变。PbCl2-6八面体A1g模和NH4+四面体A1模的拉曼频移在Tc时出现极大值。八面体T2g模、四面体T2模和外振动T2g模在Tc以下发生连续分裂。另外在Tc以下观测到对应于高温相PbCl2-6八面体T1g模的软模。

The Raman scattering measurement of ammonium hexachloroplumbate crystal has been presented. A second order structural phase transition from cubic (O5h) to trigonal structure (C23i) at Tc = 78 K was observed in this crystal. The Raman frequency shifts of the A1g mode of the PbCl2-6 octahedron and A1 mode of the ammoium tetrahedron have a maximum value at Tc Line splittings of the T2g mode of the PbCl2-6 octahedron, the Tzmodes of the ammonium tetrahedron and the external vibrational T2g mode have been observed below Tc, along with a soft mode corresponding to the T1g mode of the PbCl2-6 octahedron in the heigh temperature phase.