An infrared spectroscopic study of the internal modes of sodium nitrate: implications for the structural phase transition
An infrared spectroscopic study of the internal modes of sodium nitrate: implications for the structural phase transition
复制标题
硝酸钠内部模式的红外光谱研究：对结构相变的影响
DOI：
10.1088/0953-8984/2/25/004
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
B. Güttler
中科院分区：
文献类型：
--
作者：
M. Harris;E. Salje;B. Güttler
NaNO3 的红外活性内部模式的温度依赖性已在 77 K 至 700 K 之间进行了研究。549 K 的结构相变是通过出现附属于预期硝酸盐基团内部模式的附加峰来观察的。特别是，在 830 cm-1 处观察到比 v2 模式能量稍低的额外峰，在高于 Tc 的温度下强度急剧增加，但以牺牲 v2 模式为代价。这些结果的解释是根据序参数 P 描述的附加结构元素（与 Tc 相关）的相互作用提出的，导致三临界行为的偏差，并导致朗道势与 Q 中的序参数耦合，其中 Q 是驱动序参数，包括转变的取向有序-无序部分。进一步表明硝酸根基团的平面性在相变中起主要作用。
The temperature dependence of the infrared-active internal modes of NaNO3 has been investigated between 77 K and 700 K. The structural phase transition at 549 K is observed through the appearance of additional peaks subsidiary to the expected nitrate group internal modes. In particular, an extra peak is observed at slightly lower energies to the v2 mode at 830 cm-1, increasing dramatically in intensity at temperatures above Tc at the expense of the v2 mode. An interpretation of these results is presented in terms of the interaction of an additional structural element (which becomes relevant close to Tc) described by the order parameter P, causing a deviation from tricritical behaviour and leading to order parameter coupling in the Landau potential with Q, where Q is the driving order parameter which includes the orientational order-disorder part of the transition. It is further suggested that aplanarity of the nitrate groups plays a major part in the phase transition.