Markovian dissipative coarse grained molecular dynamics for a simple 2D graphene model.
Markovian dissipative coarse grained molecular dynamics for a simple 2D graphene model.
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DOI：
10.1063/1.4771656
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发表时间：
2012-12
期刊：
影响因子：
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通讯作者：
D. Kauzlaric;P. Español;A. Greiner;S. Succi
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文献类型：
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作者：
D. Kauzlaric;P. Español;A. Greiner;S. Succi
基于应用于石墨烯简单原子二维模型的有限元“粗粒度分子动力学”（CGMD）程序，我们建立了一个明确考虑耗散效应的石墨烯力学新粗粒度模型。结果表明，在Mori-投影算子形式中，动力学的可逆部分等效于有限温度CGMD运动方程，并且对CGMD的耗散贡献也可以包含在Mori形式中。目前石墨烯模型中的CGMD节点动量显示出明显的非马尔可夫行为，这一特性可以归因于CGMD加权函数比简单的基于质心（COM）的CG过程更有效地抑制高频模式。目前的粗粒石墨烯模型也显示出比com -变量更准确地再现动量相关函数的短时间行为，并且比COM-CG耗散更小。最后，我们发现，虽然直接由CGMD变量表示的中间时间尺度表现出明显的非马尔可夫动力学，但正模态的宏观动力学可以用马尔可夫耗散来近似，摩擦系数与波矢量的平方一样缩放。这为开发能够描述这种宏观正态模态的正确长时间行为的CGMD模型开辟了道路。
Based upon a finite-element "coarse-grained molecular dynamics" (CGMD) procedure, as applied to a simple atomistic 2D model of graphene, we formulate a new coarse-grained model for graphene mechanics explicitly accounting for dissipative effects. It is shown that, within the Mori-projection operator formalism, the reversible part of the dynamics is equivalent to the finite temperature CGMD-equations of motion, and that dissipative contributions to CGMD can also be included within the Mori formalism. The CGMD nodal momenta in the present graphene model display clear non-Markovian behavior, a property that can be ascribed to the fact that the CGMD-weighting function suppresses high-frequency modes more effectively than, e.g., a simple center of mass (COM) based CG procedure. The present coarse-grained graphene model is also shown to reproduce the short time behavior of the momentum correlation functions more accurately than COM-variables and it is less dissipative than COM-CG. Finally, we find that, while the intermediate time scale represented directly by the CGMD variables shows a clear non-Markovian dynamics, the macroscopic dynamics of normal modes can be approximated by a Markovian dissipation, with friction coefficients scaling like the square of the wave vector. This opens the way to the development of a CGMD model capable of describing the correct long time behavior of such macroscopic normal modes.