量子晶体中的原子位移
Atomic displacements in quantum crystals
摘要：
本文用量子蒙特卡罗模拟研究了低温下氦和仲氢固体中原子和分子离开晶格位置的位移。在He-3和He-4的体心立方相中，原子位移在很大程度上是量子力学性质的，即使在熔化时也是如此。计算的林德曼比熔化被认为是在良好的协议与实验结果为He-4。与氦的情况不同，在固态仲氢中，在熔化附近存在对分子振动的显着热贡献，约占总效应的一半。虽然在熔化林德曼比与实验定量一致，计算的分子均方波动功能明确的温度依赖性，与最近的实验观察不一致。
英文摘要：
Displacements of atoms and molecules away from lattice sites in helium and parahydrogen solids at low temperature have been studied by means of Quantum Monte Carlo simulations. In the bcc phases of He-3 and He-4, atomic displacements are largely quantum-mechanical in character, even at melting. The computed Lindemann ratio at melting is found to be in good agreement with experimental results for He-4. Unlike the case of helium, in solid parahydrogen there exists near melting a significant thermal contribution to molecular vibrations, accounting for roughly half of the total effect. Although the Lindemann ratio at melting is in quantitative agreement with experiment, computed molecular mean square fluctuations feature a clear temperature dependence, in disagreement with recent experimental observations.
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