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首页> 外文期刊>The Journal of Chemical Physics >Crystal structures of model lithium halides in bulk phase and in clusters
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Crystal structures of model lithium halides in bulk phase and in clusters

机译：批量相和簇中锂卤化物模型晶体结构

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摘要

We employ lattice energy calculations and molecular dynamics simulations to compare the stability of wurtzite and rock salt crystal structures of four lithium halides (LiF, LiCl, LiBr, and LiI) modeled using the Tosi-Fumi and Joung-Cheatham potentials, which are models frequently used in simulation studies. Both infinite crystals and finite clusters are considered. For the Tosi-Fumi model, we find that all four salts prefer the wurtzite structure both at 0 K and at finite temperatures, in disagreement with experiments, where rock salt is the stable structure and wurtzite exists as a metastable state. For Joung-Cheatham potentials, rock salt is more stable for LiF and LiCl, but the wurtzite structure is preferred by LiBr and LiI. It is clear that the available lithium halide force fields need improvement to bring them into better accord with the experiment. Finite-size clusters that are more stable as rock salt in the bulk phase tend to solidify as small rock salt crystals. However, small clusters of salts that prefer the wurtzite structure as bulk crystals tend to form structures that have hexagonal motifs, but are not finite-size wurtzite crystals. We show that small wurtzite structures are unstable due to the presence of a dipole and rearrange into more stable, size-dependent structures. We also show that entropic contributions can act in favor of the wurtzite structure at higher temperatures. The possible relevance of our results for simulation studies of crystal nucleation from melts and/or aqueous solutions is discussed. Published by AIP Publishing.
机译：我们采用格子能量计算和分子动力学模拟，以比较使用TOSI-Fumi和Joung-Cheatham电位建模的四个卤化物（LiF，LiCL，LiBr和LiZ）的抗卤素和岩盐晶体结构的稳定性，这些模型经常是型号用于仿真研究。考虑无限晶体和有限簇。对于TOSI-FUMI模型，我们发现所有四种盐都喜欢在0 k和有限温度下的紫立塔结构，在不同的实验中，岩盐是稳定的结构，紫吨石作为亚稳态存在。对于joung-cheatcham电位，LiF和LiCl的岩盐更稳定，但紫立塔结构是由LIBL和LII的优选。很明显，可用的卤化锂力田需要改善，使其更好地符合实验。随着岩盐相中岩盐岩盐的有限簇越稳定，倾向于凝固为小岩盐晶体。然而，更喜欢卟啉结构的小植物，作为散装晶体倾向于形成具有六边形基序的结构，但不是有限尺寸的纯晶体。我们表明，由于偶极子和重新排列成更稳定，尺寸依赖的结构，小紫立塔结构是不稳定的。我们还表明，熵贡献可以在更高的温度下引起抗卧位结构。讨论了我们对熔融和/或水溶液的晶体成核的模拟研究结果的可能相关性。通过AIP发布发布。

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