Zhonghan Hu

E-mail: zhonghanhu_ATA_email._sdu._edu._cn (Please remove _ and change ATA to @)

Research Description:

Statistical mechanics relates macro- and meso-scopic observations, either in a real experiment or in an artificial numerical simulation, to micro-scopic interactions and dynamics. In order to make such a relation powerful and predictive, one may introduce certain approximations to simplify the statistical formulations in the framework. The symmetry-preserving mean-field (SPMF) approximation that I am primarily working on [1] follows the mean-field ideas by Johannes van der Waals, Benjamin Widom, and John Weeks, which split the total microscopic interaction into the short-ranged rapidly varying and long-ranged slowly varying components and then treat them separately. The SPMF approach further suggests that certain slowly varying component can be replaced by its average over the degrees of the freedom with preserved symmetry[1,2].

  This approach naturally leads to accurate and efficient methods for numerical simulations of condensed phases by using the known symmetries and boundary conditions as guiding constrains. Given the clear physical picture of a problem, the mean-field approach may even provides simple, intuitive and transparent understanding of the underlying mechanism.

As a particular example, SPMF has been applied to the problem of proper treatments of electrostatics in molecular simulations[3,4]. When the lattice sum formulation (e.g. Ewald sums [5,6,7]) for electrostatics under periodic boundary conditions are formulated as a pairwise interaction[8,9], the difference between the defined pairwise interaction and the Coulomb interaction is regarded as a slowly varying components. Under the spherical symmetry, the average effect of this slowly varying component vanishes, which therefore justifies the use of the Ewald sum method with tinfoil boundary condition for simulations of bulk and spherical interfaces[3]. On the other hand, corrections are necessary when charges or polar molecules are placed on planar walls[3,4]. In addition, when the dielectric constant is sufficient to describe the response of the dielectric material to an external electric field or a charged wall, the mean-field theory predicts analytically the finite-size effect in supercell modelling of charged interfaces, which was confirmed by the numerical simulations in the literature[4].

Representative Publications:

[1].Zhonghan Hu (2014) “Symmetry-preserving mean field theory for electrostatics at interfaces” Chem. Commun. 50, 14397

[2]. Shasha Yi; Cong Pan; Liming Hu; and Zhonghan Hu (2017) “On the connections and differences among three mean-field approximations: a stringent test”, Phys. Chem. Chem. Phys. 19, 18514

[3]. Cong Pan; Shasha Yi; and Zhonghan Hu (2017) “The Effect of electrostatic boundaries in molecular simulations: symmetry matters”, Phys. Chem. Chem. Phys. 19, 4861

[4]. Cong Pan; Shasha Yi; and Zhonghan Hu (2019) “Analytic theory of finite-size effects in supercell modelings of charged interfaces”, Phys. Chem. Chem. Phys. 21, 14858

[5]. Shasha Yi; Cong Pan; and Zhonghan Hu (2015) “Accurate treatments of electrostatics for computer simulations of biological systems: A brief survey ofdevelopments and existing problems” Chin. Phys. B, 24, 120201

[6]. Cong Pan; and Zhonghan Hu (2014) “Rigorous Error Bounds for Ewald Summation of Electrostatics at Planar Interfaces”, J. Chem. Theory Comput. 10, 534

[7]. Cong Pan; and Zhonghan Hu (2015) “Optimized Ewald sum for electrostatics in molecular self-assembly systems at interfaces” Sci. China Chem. 58, 1044

[8]. Zhonghan Hu (2014) “Infinite boundary terms of Ewald sums and pairwise interactions for electrostatics in bulk and at interfaces”, J. Chem. Theory Comput. 10, 5254

[9]. Shasha Yi; Cong Pan; and Zhonghan Hu (2017) “Note: A pairwise form of the Ewald sum for non-neutral systems”, J. Chem. Phys., 147,126101

A Full List of Publications:

https://orcid.org/0000-0003-4879-2775

https://publons.com/researcher/2768853/zhonghan-hu

Group Members: