- Development of Accurate Effective Force Field From ab initio Molecular Dynamics Simulation Using Coarse-graining Approach
Computer simulation methods have become more popular in predicting properties of complex systems with recent advances in high-performance computing. When provided with an accurate force field a computer simulation approach will accurately predict properties of a system of interest. Quantum-mechanical (QM) methods deliver the most reliable and accurate properties prediction by taking into account the electronic behavior from first principles. However, QM approaches are computationally expensive and typically used with smaller systems. Classical or molecular mechanics methods are much faster but less accurate due to use of empirical force fields. The focus of this project is to coarse-grain the electronic structure out of a system, but maintain all of the atoms, thus converting a quantum atomistic molecule into a classical atomistic molecule by coarse-graining. In conventional coarse-graining approaches the effect of the electron structure is averaged out and represented in the form of pair interaction mean forces so that relevant timescale information is lost. This leads to inaccurate predictions of the dynamics and transport properties. A novelty of the proposed project is in the application of recently developed coarse-graining approach to recover timescales lost during a coarse-graining procedure. As a result of this project, an accurate force field for the classical atomistic system will be developed based on first principles ab initio method. This will allow one to perform large-scale atomistic simulations with QM-accuracy. The target system of this project is the suite of heterogeneous catalysts called mesoporous silica nanoparticles that are synthesized and studied theoretically in the Ames Laboratory.
Mentor: Mark Gordon, distinguished professor of Chemistry, Iowa State University
- N-Doped Nanoporous Carbon Monolith Synthesis and the Application for Electrocatalysis
Doping nitrogen within porous carbon skeleton has been demonstrated that it is a powerful approach to tuning electronic properties and/or conductivity, which thus facilitate their applications, particularly in electrocatalysis. Meanwhile, the electrocatalysis performance of N-doped carbon materials strongly depends on the density of the active sites and how these active sites are distributed in the skeleton. Thus, the development of new synthetic methods is the key for creation of advanced N-doped carbon materials for electrocatalysis. In order to prepare N-doped carbon catalysts, herein we propose to develop a novel synthetic methodology which includes a template-free synthesis of polymeric monolith precursors and afterward high temperature carbonation step.
There are four innovations involved in this project. First, a facile method will be used to prepare polymer precursors based on one step radical polymerization without any template agents. The porous monolithic polymer precursor can be converted to carbon monoliths with uniform nitrogen decoration and high porosity of precursors can be partially preserved to afford high surface area of resultant carbons via facile pyrolysis. The second innovation is the high surface area and nanosized pores guarantee the free diffusion of oxygen and electrolyte to the catalytic active sites through short diffusion path lengths. The third innovation involves improvements in electrocatalysis with a homogeneous distribution of nitrogen atoms. Finally, the monolithic N-doped carbon, compared to carbon powder, can be easily recovered and reused for many times. This should form the foundation for a new generation of high surface area carbon catalysts for electrocatalysis.
Mentor: Wenyu Huang, assistant professor of chemistry, Iowa State University