含杂质球偶极子铁电玻璃：极性纳米区、外加电场响应和遍历击穿
Ferroelectric glass of spheroidal dipoles with impurities: Polar nanoregions, response to applied electric field, and ergodicity breakdown
摘要：
利用分子动力学模拟，我们研究了偶极玻璃晶体中的微球形，极性粒子和球形，金属壁之间的非极性杂质。我们提出的物理图片的铁电玻璃，这已被观察到的弛豫，混合晶体（如KCN $_x$ KBr $_{1-x}$），和聚合物。我们的系统在很宽的温度范围内进行扩散过渡，在那里我们看到被杂质包围的极性纳米区（PNR）。在我们的模拟中，杂质形成团簇，它们的空间分布是不均匀的。极化波动在相对高的$T$下增强，这取决于偶极矩的大小。当$T$进一步降低到非遍历状态时，它们形成冻结的PNR。因此，介电常数表现出弛豫铁电体的特征。我们还研究了周期性施加电场的非线性响应和周期性温度变化的非遍历响应（ZFC $/$ FC），其中极化和应变集体和不均匀地变化。我们还研究了由分子形状不对称引起的反铁电玻璃。我们用Ewald方法计算了外加电场中的偶极相互作用。
英文摘要：
Using molecular dynamics simulation, we study dipolar glass in crystals composed of slightly spheroidal, polar particles and spherical, apolar impurities between metal walls. We present physical pictures of ferroelectric glass, which have been observed in relaxors, mixed crystals (such as KCN$_x$KBr$_{1-x}$), and polymers. Our systems undergo a diffuse transition in a wide temperature range, where we visualize polar nanoregions (PNRs) surrounded by impurities. In our simulation, the impurities form clusters and their space distribution is heterogeneous. The polarization fluctuations are enhanced at relatively high $T$ depending on the size of the dipole moment. They then form frozen PNRs as $T$ is further lowered into the nonergodic regime. As a result, the dielectric permittivity exhibits the characteristic features of relaxor ferroelectrics. We also examine nonlinear response to cyclic applied electric field and nonergodic response to cyclic temperature changes (ZFC$/$FC), where the polarization and the strain change collectively and heterogeneously. We also study antiferroelectric glass arising from molecular shape asymmetry. We use an Ewald scheme of calculating the dipolar interaction in applied electric field.
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