Incorporation of quantum statistical features in molecular dynamics.
Incorporation of quantum statistical features in molecular dynamics.
复制标题
将量子统计特征纳入分子动力学。
DOI：
10.1103/physrevlett.75.596
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发表时间：
1995
影响因子：
8.6
通讯作者：
Randrup
中科院分区：
文献类型：
--
作者：
Ohnishi;Randrup
分子动力学模拟对于理解各种物理背景下多体系统的统计和动力学性质都很有用[1]。虽然在许多情况下可以获得定量的洞察力，但当涉及量子系统时，这种方法的基础和解释是有问题的。在这些方法中，多体系统通常被表示为参数化单粒子波包的（可能反对称化的）产物，然后从合适的变分原理导出参数的运动方程。这对应于量子问题的平均场处理，随后的参数动力学则是eectively经典的。因此，该系统的统计特性将是经典的，而不是量子的，从而对量子统计起着重要作用的复杂系统中获得的结果的定量效用产生怀疑。分子动力学的这种普遍缺点源于忽略了与波包相关的能量本征值的谱分布，这些波包不是能量本征态[2]。在本说明中，我们提出了一种可能的方法，通过这种方法可以在很大程度上缓解这一固有问题。这种新的方法包括在动力学中引入一个随机项，使一个给定的波包可以根据其谱分布自发跃迁到相邻的波包，它被发现，随之而来的diusive演化与此项表现出松弛的量子统计平衡。该方法相当普遍，因此应该具有相应的广泛兴趣。
Molecular dynamics simulations are useful for understanding both statistical and dynamical properties of many-body systems in a variety of physical contexts [1]. While quantitative insight can be obtained in many cases, the foundation and interpretation of such approaches are problematic when quantum systems are addressed. In these approaches the many-body system is usually represented as a (possibly antisymmetrized) product of parametrized single-particle wave packets, and equations of motion for the parameters are then derived from a suitable variational principle. This corresponds to a meanfield treatment of the quantal problem and the ensuing parameter dynamics is then eectively classical. Consequently, the statistical properties of the system will be classical rather than quantal, thus casting doubt on the quantitative utility of results obtained in complicated scenarious where quantal statistics plays a major role. This generic shortcoming of molecular dynamics originates in the neglect of the spectral distribution of energy eigenvalues associated with the wave packets which are not energy eigenstates [2]. In the present note we suggest a possible method by which this inherent problem can be largely alleviated. This novel method consists of introducing a stochastic term in the dynamics so that a given wave packet may make spontaneous transitions to neighboring wave packets in accordance with its spectral distribution, and it is found that the ensuing diusive evolution with this term exhibits relaxation towards quantum-statistical equilibrium. The method is rather general and so it should be of correspondingly broad interest.