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Low-temperature anharmonicity of barium titanate: A path-integral molecular-dynamics study

机译:钛酸钡的低温非谐性:路径积分的分子动力学研究

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摘要

We investigate the influence of quantum effects on the dielectric and piezoelectric properties of barium titanate in its (low-temperature) rhombohedral phase, and show the strongly anharmonic character of this system even at low temperature. For this purpose, we perform path-integral molecular-dynamics simulations under fixed pressure and fixed temperature, using an efficient Langevin thermostat-barostat, and an effective Hamiltonian derived from first-principles calculations. The quantum fluctuations are shown to significantly enhance the static dielectric susceptibility (≈ by a factor of 2) and the piezoelectric constants, reflecting the strong anharmonicity of this ferroelectric system even at very low temperature. The slow temperature-evolution of the dielectric properties observed below ≈100 K is attributed (i) to zero-point energy contributions and (ii) to harmonic behavior if the quantum effects are turned off.
机译:我们研究了量子效应对钛酸钡(低温)菱面体相的介电和压电性能的影响,并显示了即使在低温下该体系的强非谐特性。为此,我们使用有效的Langevin恒温恒压器和从第一性原理计算得出的有效哈密顿量,在固定压力和固定温度下进行路径积分分子动力学模拟。量子涨落被证明可以显着提高静态介电常数(≈2倍)和压电常数,从而反映出该铁电系统即使在非常低的温度下也具有很强的非谐性。在≈100K以下观察到的介电特性的缓慢温度演变是由于(i)零点能量贡献和(ii)如果关闭了量子效应而引起的谐波行为。

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  • 来源
    《Physical review》 |2013年第1期|014113.1-014113.9|共9页
  • 作者单位

    CEA, DAM, DIF, F-91297 Arpajon, France;

    Laboratoire Structures, Proprietes et Modelisation des Solides, Centre National de la Recherche Scientifique Unite Mixte de Recherche 8580,Ecole Centrale Paris, F-92295 Chatenay-Malabry, France, and Laboratoire des Solides lrradies, Ecole Polytechnique, Commissariat a l'Energie Atomique, Centre National de la Recherche Scientifique, F-91128 Palaiseau, France;

    Laboratoire des Solides lrradies, Ecole Poly technique, Commissariat a l'Energie Atomique, Centre National de la Recherche Scientifique,F-91128 Palaiseau, France;

    Laboratoire Structures, Proprietes et Modelisation des Solides, Centre National de la Recherche Scientifique Unite Mixte de Recherche 8580,Ecole Centrale Paris, F-92295 Chatenay-Malabry, France;

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  • 正文语种 eng
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  • 关键词

    computational methods in statistical physics and nonlinear dynamics; dielectric, piezoelectric, ferroelectric, and antiferroelectric materials;

    机译:统计物理和非线性动力学的计算方法;电介质;压电;铁电和反铁电材料;

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