Possible Disorder of the P Atom in KD2PO4
Possible Disorder of the P Atom in KD2PO4
复制标题
KD2PO4 中 P 原子可能的紊乱
DOI：
10.1209/0295-5075/13/2/008
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发表时间：
1990
期刊：
影响因子：
1.8
通讯作者：
W. Kuhs
中科院分区：
文献类型：
--
作者：
M. McMahon;R. Nelmes;R. Piltz;W. Kuhs
在Tc + 5k下从KD2PO4 （DKPD）获得了高分辨率的中子衍射数据。对这些数据的分析表明，p原子的分布是高度非调和的，以至于它可以被建模为三个位置上的无序——一个中心位置在平均位置，另外两个位置沿着±z对称地位移，其中z是在Tc以下的低温铁电（FE）相的极轴方向。位移位点对应于PO4基团的两个FE构型。结果表明，各遗址的种群数量为40%，而中心遗址的种群数量仅为20%。这表明在Tc以上的FE构型比这类相变的标准模型所预测的优势要大得多。
Very high-resolution neutron diffraction data have been collected from KD2PO4 (DKPD) at Tc + 5 K. Analysis of these data shows that the P-atom distribution is highly anharmonic, so much so that it can be modelled as disorder over three sites–a central site at the mean position, and two others displaced symmetrically along ±z, where z is the direction that becomes the polar axis of the low-temperature ferroelectric (FE) phase below Tc. The displaced sites correspond to the two FE configurations of the PO4 groups. It is concluded that the population of these sites is 40% in each, leaving only 20% at the central site. This indicates a much greater preponderance of the FE configurations just above Tc than predicted by the standard model of phase transitions of this type.