Absolute Entropy and Free Energy of Pure Substances from Molecular Dynamics Simulations Using the Two-Phase Thermodynamic Model
Date Issued
2011
Date
2011
Author(s)
Huang, Shao-Nung
Abstract
Presented in this thesis is a novel approach for calculating the free energy and absolute entropy of pure substances from molecular dynamic (MD) simulations based on the two-phase thermodynamic (2PT) method. This efficient method provides converged properties from a very short (20 ps) MD trajectory. The 2PT method determines thermodynamic properties by weighed integral of the density of state (velocity spectrum); the applied weighing functions are obtained from the statistical mechanical theories. The contribution of the density of state from its components, which are associated with their corresponding molecular motions, allows for the evaluation of the dynamical behaviors of fluids or solids. In this study, the accuracy of 2PT thermodynamic properties (absolute entropy, internal energy, heat capacity, etc.) is investigated from the triple point to the critical point along the vapor-liquid coexisting curve for water and carbon dioxide. Also presented are the prediction of coexistence curves of water and carbon dioxide through free energy equalities. Our results show that the 2PT properties are highly accurate, with its results comparable to other rigorous methods, such as the free energy perturbation method. It can be concluded that 2PT method is a matured way that is applicable to various fields and more complicated systems in the near future.
Subjects
Density of State
Entropy
Free Energy
Phase Diagram
Molecular Dynamics Simulations
Type
thesis
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