Molecular simulation is an essential tool for interpreting and predicting the structure, thermodynamics, and dynamics of chemical and biochemical systems. The fundamental inputs into these simulations are the intra- and intermolecular force fields, which provide simple and computationally efficient descriptions of molecular interactions. (By force field, we mean a set of parameters and equations used to model the potential energy surface of a sytem). Consequently, the predictive and explanatory power of molecular simulations depends on the fidelity of the force field to the underlying (exact) potential energy surface. Because the development of high-quality force fields is so essential to accurate molecular simulation, a major focus of our group is on improving the force field development process, with a particular emphasis on studying intermolecular interactions. Our methodology is centered on "physically-motivated" force field development, with the hypothesis that we can craft highly accurate, broadly applicable, and easy-to-develop intermolecular force fields by requiring that the parameters and equations used in our models are closely derived from the underlying physics of intermolecular interactions. (See Schmidt, 2015; VanVleet, 2016; McDaniel, 2014; McDaniel, 2013; Yu, 2011 for more details)
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Using our "physically-motivated" force field development methodology (here termed Slater-ISA), we are able to generate force fields that are both highly accurate (as demonstrated by the good reproduction of high-level ab initio benchmark energies computed from SAPT) and that are insensitive to the details of force field parameterization, especially compared to previous approaches (here termed Born-Mayer-IP). See VanVleet, 2016 for original figure and details.
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In the process of improving intermolecular force fields, our group has simultaneously sought to apply our methodology to a variety of real-world applications, ranging from gas separation in metal-organic frameworks (see McDaniel, 2015; McDaniel, 2012; Yu, 2011) to structural and dynamic properties of ionic liquids (see McDaniel, 2016; Son, 2016) and neat organic liquids (see McDaniel, 2013). Future applications of our force fields will include MOF nucleation and growth as well as biomolecular simulation.
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CO2 gas adsorption isotherms at 298 K for selected metal-organic frameworks (MOFs). Simulation results (symbols) are compared with corresponding experimental values (lines). See Schmidt, 2015 for original figure and details.
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By combining methodological advances with timely applications to problems in chemical and materials science, we hope work in our group will significantly broaden and improve the scope of molecular simulation.
References:
1) Schmidt J.R, Yu K, McDaniel J. 2015. Transferable Next-Generation Force Fields from Simple Liquids to Complex Materials. Accounts of Chemical Research. 48(3):548–556.
2) Van Vleet MJ, Misquitta AJ, Stone AJ, Schmidt J.R. 2016. Beyond Born–Mayer: Improved Models for Short-Range Repulsion in ab Initio Force Fields. J. Chem. Theory Comput. Article ASAP
3) McDaniel J, Schmidt J.R. 2014. First-Principles Many-Body Force Fields from the Gas Phase to Liquid: A “Universal” Approach. The Journal of Physical Chemistry B. 118(28):8042–8053.
4) McDaniel J, Schmidt J.R. 2013. Physically-Motivated Force Fields from Symmetry-Adapted Perturbation Theory. The Journal of Physical Chemistry A. 117(10):2053–2066.
5)Yu K, Schmidt J.R. 2011. Elucidating the Crystal Face- and Hydration-Dependent Catalytic Activity of Hydrotalcites in Biodiesel Production. The Journal of Physical Chemistry C. 115(5):1887-1898.
6) McDaniel J, Li S, Tylianakis E, Snurr RQ, Schmidt J.R. 2015. Evaluation of Force Field Performance for High-Throughput Screening of Gas Uptake in Metal-Organic Frameworks. Journal of Physical Chemistry C. 119(6):3143–3152.
7) McDaniel J, Schmidt J.R. 2012. Robust, Transferable, and Physically Motivated Force Fields for Gas Adsorption in Functionalized Zeolitic Imidazolate Frameworks. The Journal of Physical Chemistry C. 116(26):14031-39.
8) McDaniel J, Choi E, Son C-Y, Schmidt J.R, Yethiraj A. 2016. Conformational and Dynamic Properties of Poly(ethylene oxide) in an Ionic Liquid: Development and Implementation of a First-Principles Force Field. Journal of Physical Chemistry B. 120(1):231-243.
9) Son CYun, McDaniel JGatten, Schmidt JR, Cui Q, Yethiraj A. 2016. First Principles United Atom Force Field for the Ionic Liquid [BMIM][BF4] : An Alternative to Charge Scaling. J. Phys. Chem B. 120(14):3560-3568.