We present a new theoretical method for efficient calculation of free energy of liquid. This interaction entropy method allows one to compute entropy and free energy of liquid from standard single step MD(molecular dy...We present a new theoretical method for efficient calculation of free energy of liquid. This interaction entropy method allows one to compute entropy and free energy of liquid from standard single step MD(molecular dynamics) simulation directly in liquid state without the need to perform MD simulations at many intermediate states as required in thermodynamic integration or free energy perturbation methods. In this new approach, one only needs to evaluate the interaction energy of a single(fixed) liquid molecule with the rest of liquid molecules as a function of time from a standard MD simulation of liquid and the fluctuation of distribution of this interaction energy is then used to calculate the interaction entropy of the liquid. Explicit theoretical derivation of this interaction entropy approach is provided and numerical calculations for the benchmark liquid water system were carried out using three different water models. Numerical analysis of the result was performed and comparison of the computational result with experimental data and other theoretical results were provided. Excellent agreement of calculated free energies with the experimental data using TIP4 P model is obtained for liquid water.展开更多
The thermodynamical properties of MgCl_2 in KCI-MgCl_2-LiCl molten electrolytes containing MgCl_2 below 0.5 (mole fraction, the same below) have been determined from the interchange energies of two binary systems KCI...The thermodynamical properties of MgCl_2 in KCI-MgCl_2-LiCl molten electrolytes containing MgCl_2 below 0.5 (mole fraction, the same below) have been determined from the interchange energies of two binary systems KCI-MgCl_2 and LiCI-MgCl_2, by means of a model on the assumptions that the electrolytes in the solution are treated as independent particles instead of their ion forms and the interchange energy between the component pair KCI-LiCl is ignored when compared with those of component pairs KCl-MgCl_2 and MgCl_2-LiCl. The interchange energies, wKCl-MgCl_2 and wMgcCl_2-Licl, are obtained as-70000 and -13800 J.mol-1, from the corresponding binary solutions, respectively.展开更多
Spontaneous rupture of some polymer films upon heating is commonplace. The very criterion for this instability is the system free energy possessing a negative curvature. Within the framework of full frequency-dependen...Spontaneous rupture of some polymer films upon heating is commonplace. The very criterion for this instability is the system free energy possessing a negative curvature. Within the framework of full frequency-dependent theory of dispersion forces, we have derived the excess free energy of a typical system--polystyrene film deposited on the silicon substrate. The excess free energy, wavelengths and growth rates are calculate and a comparison is made between the accurate results and the approximate results. It is found that the stability of the fihn can be tuned by the variation of the thickness of the coating and the retardation effects can be significant sometimes.展开更多
基金supported by the National Natural Science Foundation of China (21603144, 21433004)Ministry of Science and Technology of China (2016YFA0501700)+1 种基金NYU Global Seed Grant, Shanghai Putuo District (2014-A-02)Shanghai Sailing Program (2016YF1408400)
文摘We present a new theoretical method for efficient calculation of free energy of liquid. This interaction entropy method allows one to compute entropy and free energy of liquid from standard single step MD(molecular dynamics) simulation directly in liquid state without the need to perform MD simulations at many intermediate states as required in thermodynamic integration or free energy perturbation methods. In this new approach, one only needs to evaluate the interaction energy of a single(fixed) liquid molecule with the rest of liquid molecules as a function of time from a standard MD simulation of liquid and the fluctuation of distribution of this interaction energy is then used to calculate the interaction entropy of the liquid. Explicit theoretical derivation of this interaction entropy approach is provided and numerical calculations for the benchmark liquid water system were carried out using three different water models. Numerical analysis of the result was performed and comparison of the computational result with experimental data and other theoretical results were provided. Excellent agreement of calculated free energies with the experimental data using TIP4 P model is obtained for liquid water.
基金National Natural Science Foundation of China!No.59774028
文摘The thermodynamical properties of MgCl_2 in KCI-MgCl_2-LiCl molten electrolytes containing MgCl_2 below 0.5 (mole fraction, the same below) have been determined from the interchange energies of two binary systems KCI-MgCl_2 and LiCI-MgCl_2, by means of a model on the assumptions that the electrolytes in the solution are treated as independent particles instead of their ion forms and the interchange energy between the component pair KCI-LiCl is ignored when compared with those of component pairs KCl-MgCl_2 and MgCl_2-LiCl. The interchange energies, wKCl-MgCl_2 and wMgcCl_2-Licl, are obtained as-70000 and -13800 J.mol-1, from the corresponding binary solutions, respectively.
基金Project supported by the Natural Science Foundation of Hu＇nan Province, China （Grant No 00JJY2072）, and the Foundation of Educational Committee of Hu＇nan Province, China （Grant Nos 00C189 and 01B019）.
文摘Spontaneous rupture of some polymer films upon heating is commonplace. The very criterion for this instability is the system free energy possessing a negative curvature. Within the framework of full frequency-dependent theory of dispersion forces, we have derived the excess free energy of a typical system--polystyrene film deposited on the silicon substrate. The excess free energy, wavelengths and growth rates are calculate and a comparison is made between the accurate results and the approximate results. It is found that the stability of the fihn can be tuned by the variation of the thickness of the coating and the retardation effects can be significant sometimes.
