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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Energy landscapes of quantum Lennard-Jones solids
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Energy landscapes of quantum Lennard-Jones solids

机译：量子伦纳德-琼斯固体的能态

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摘要

To generalize inherent structure analysis to understand structural changes in quantum liquids and solids, differences between classical (V(x)) and quantum-corrected (U_(qeff)(x)) energy landscapes are estimated as a function of the de Boer parameter (?). Path integral simulations of quantum Lennard-Jones solids are performed at zero pressure and a dimensionless reduced temperature of 0.123, corresponding to an absolute temperature of 4.2K. At constant temperature and pressure, ? is increased from the classical limit of zero to ? = 0.28, corresponding to para-H2. Increasing quantum delocalization effects result in a continuous decrease in density and local order but without a transition to a disordered, liquid state. The inherent structure landscape of bulk systems is strongly dependent on density with the energy and stability of crystalline minima decreasing relative to that of amorphous packing minima as the system is stretched. For ? ≈ 0.23, the volume fluctuations in quantum solids are sufficient to result in sampling of disordered minima while for ? = 0.28, the underlying classical inherent structures are completely disordered, indicating that the topography of U _(qeff)(x) and V(x) are qualitatively different for such values of ?. To assess the nature of the quantum-corrected energy landscape, effective pair potentials are defined by u_(qeff)(r) = -kT ln g(r) using the pair correlation function (g(r)) of the quantum system in the neighborhood of the first peak. Our results show that as ? increases, the pair potentials become increasingly softer, shallower, and of increasing range with a shifting of the potential minimum to larger distances. For example, the reduction of the entropy of fusion and melting temperatures of quantum solids with increasing ? are analogous to the changes in thermodynamics of melting seen in classical solids with increasing range and softness of interactions. The energy landscapes associated with such coarse-grained potentials should be useful as predictors of structural transformations in quantum systems, analogous to their use in understanding phase diagrams of complex fluids.
机译：为了概括内在结构分析以了解量子液体和固体中的结构变化，经典（V（x））和量子校正（U_（qeff）（x））能量态势之间的差异根据de Boer参数（ ？）。量子Lennard-Jones固体的路径积分模拟是在零压力和0.123的无量纲降低的温度（相当于4.2K的绝对温度）下进行的。在恒定温度和压力下，从经典的零极限增加到？ = 0.28，对应于对H2。越来越多的量子离域效应导致密度和局部顺序的连续降低，但没有过渡到无序的液态。本体系统的固有结构格局在很大程度上取决于密度，随着系统的拉伸，相对于无定形堆积的最小值，结晶最小值的能量和稳定性降低。为？ ≈0.23，量子固体中的体积波动足以导致无序极小值的采样，而对于？ = 0.28，则基本的经典固有结构完全无序，这表明U _（qeff）（x）和V（x）的形貌在质量上不同于。为了评估量子校正后的能量态势的性质，有效量子对势由u_（qeff）（r）= -kT ln g（r）定义，使用量子系统中的量子对相关函数（g（r））。第一个高峰附近。我们的结果表明为？随着电势最小值的增加到更大的距离，线对电位变得越来越软，更浅并且范围越来越大。例如，量子熵的融合熵和熔化温度的降低随α的增加而降低。与经典固体中熔融热力学的变化类似，随着相互作用范围和柔软度的增加而变化。与此类粗粒度电势相关的能量格局应可用作量子系统中结构转换的预测器，类似于它们在理解复杂流体的相图中的使用。

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