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摘要翻译：
本文用Landau热力学势描述了BaTiO_3单晶的介电和铁电性质。我们的结果表明，当使用热力学势的六次自由能展开式时，需要显著不同的四次系数β(p^4_i项系数）才能分别充分再现顺电相和电场诱导铁电相的非线性介电行为。相反，八次方展开与一个共同的系数集能够很好地描述这两个阶段在同一时间。这些特征与文献资料一起，有力地证明了BaTiO_3的Landau热力学势中存在八次方项的必要性。另外，从顺电相[001]、[011]和[111]方向的非线性介电响应计算了四次方系数\β和\Xi（p^2_i p^2_j项系数）。在T_c以上，这两个系数都有明显的温度依赖性。对四方相中单畴晶体的线性介电响应的进一步分析表明，与温度有关的非谐系数对于充分描述铁电相中的介电行为也是必要的。因此，我们提出了一个八次方热力学势，其中一些非谐系数与温度有关，并与已有的势进行了比较。总的来说，本工作中提出的电势在再现这种原型铁电物质的介电和铁电性质方面表现出较高的质量。
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英文标题：
《Landau thermodynamic potential for BaTiO_3》
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作者：
Y. L. Wang, A. K. Tagantsev, D. Damjanovic, N. Setter, V. K.
Yarmarkin, A. I. Sokolov, and I. A. Lukyanchuk
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最新提交年份：
2007
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分类信息：
一级分类：Physics 物理学
二级分类：Statistical Mechanics 统计力学
分类描述：Phase transitions, thermodynamics, field theory, non-equilibrium phenomena, renormalization group and scaling, integrable models, turbulence
相变，热力学，场论，非平衡现象，重整化群和标度，可积模型，湍流
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一级分类：Physics 物理学
二级分类：Materials Science 材料科学
分类描述：Techniques, synthesis, characterization, structure. Structural phase transitions, mechanical properties, phonons. Defects, adsorbates, interfaces
技术，合成，表征，结构。结构相变，力学性质，声子。缺陷，吸附质，界面
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英文摘要：
In the paper, the description of the dielectric and ferroelectric properties of BaTiO_3 single crystals using Landau thermodynamic potential is addressed. Our results suggest that when using the sixth-power free energy expansion of the thermodynamic potential, remarkably different values of the fourth-power coefficient, \beta (the coefficient of P^4_i terms), are required to adequately reproduce the nonlinear dielectric behavior of the paraelectric phase and the electric field induced ferroelectric phase, respectively. In contrast, the eighth-power expansion with a common set of coefficients enables a good description for both phases at the same time. These features, together with the data available in literature, strongly attest to the necessity of the eighth-power terms in Landau thermodynamic potential of BaTiO_3. In addition, the fourth-power coefficients, \beta and \xi (the coefficient of P^2_i P^2_j terms), were evaluated from the nonlinear dielectric responses along [001], [011], and [111] orientations in the paraelectric phase. Appreciable temperature dependence was evidenced for both coefficients above T_C. Further analysis on the linear dielectric response of the single domain crystal in the tetragonal phase demonstrated that temperature dependent anharmonic coefficients are also necessary for an adequate description of the dielectric behavior in the ferroelectric phase. As a consequence, an eighth-power thermodynamic potential, with some of the anharmonic coefficients being temperature dependent, was proposed and compared with the existing potentials. In general, the potential proposed in this work exhibits a higher quality in reproducing the dielectric and ferroelectric properties of this prototypic ferroelectric substance.
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PDF链接：
https://arxiv.org/pdf/706.3261
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