Our research program encompasses the development of chemical simulation methods and the application of those methods to problems of practical interest. Our research is driven primarily by applied interests, with an emphasis on developing a detailed understanding of phenomena that are relevant to emerging real-world technological applications. The applied component of our research is focused on understanding the processes in sliding contacts and exploring nickel-based electrocatalysts. The method development component of our research is done to support our applied research efforts. Our method development efforts are focused on developing techniques to extend the time-scales accessible in molecular dynamics simulations of reactions and reducing the computational effort associated with including exact exchange in quantum chemical calculations of periodic systems.
Work by our group has led to a better understanding of friction and wear, the effects of stress on reactivity, the structures of chiral materials and self-assembled systems, and the role of solvent and catalysts in reactions, methods for treating strongly-correlated electron materials, and constitutive models that connect properties obtained through calculations to real-world systems. This work has been published in top-level journals such as Science, Nature Chemistry, Nature Communications, Nature Scientific Reports, Physical Review Letters, Journal of the American Chemical Society, and Angewandte Chemie, has been covered in media such as Canadian Chemical News and Chemical & Engineering News, and has led to funding from NSERC and the Ontario government, and consulting relationships with corporations such as Xerox and Exxon-Mobil.
Our research is highly multidisciplinary, combining aspects of chemistry, physics, materials science, mathematics, computer science, and engineering. As such, members of the group gain skills in a wide range fo areas, which may be useful in their future careers. Researchers interested in joining our group should contact Dr. Mosey.
Tenure application reviewer
Friction and wear impact the functionality, efficiency, and longevity of all devices containing sliding contacts, with substantial economic and environment impacts. Estimates place the cost of friction and wear at ~5% of the GDP in industrialized nations;10 equivalent to ~$120B annually in Canada. Friction leads to energy losses, placing greater demands on finite energy resources, while wear of devices increases waste. Lubricants mitigate these deleterious effects; however, lubrication is not presently an exact science and relies largely on variations on known lubricants or trial-and-error. As such, lubrication is not optimal in a broad sense, and lubrication strategies are lacking for emerging technologies such as miniaturized devices.
The development of improved lubrication strategies requires a detailed understanding of the atomic-level origins of friction and wear. Our group uses chemical simulations for the purposes of gaining such insights. While friction has been studied for decades with simulations, our group is largely unique in using first-principles molecular dynamics simulations to study friction and wear. The ability to described sliding induced changes in bonding through these simulations has shed light on fundamental details of friction and wear, allowed us to suggest new lubrication paradigms, and has led to improve friction laws.
Our present research in this area involves using simulations to explore the properties of friction modifiers, protective carbene-based coatings, and low-friction two-dimensional hydrogen bonded networks. In addition, our group develops analytical models that connect the results of our simulations to real-world properties and phenomena.
We are part of a collaborative effort supported by an NSERC Discovery Frontiers grant involving that aims to to create affordable, alkaline fuel cells for the production of energy; develop new technologies for hydrogen-based energy storage; and transform glycerol into value-added chemicals that will make biodiesel production cheaper and greener. While alkaline fuel cells have been used for a long time (for instance, these fuel cells were used in the Apollo missions), this research program is is focused on developing nickel materials that will be used in new alkaline fuel cell technologies that will assist Canada in transitioning to the hydrogen economy.
This research area involves 14 Canadian researchers, seven universities (Queen’s University, University of Victoria, Simon Fraser University, INRS Université de Recherche, University of Toronto, University of Ottawa and McMaster University), nine international researchers from seven countries, and a number of industry partners. This group’s expertise covers a wide a range of research areas, with groups performing computational chemistry, materials science, polymer engineering, and fuel cell design and fabrication.
Our efforts in this area are focused on using quantum chemical calculations, particularly density functional theory and tight-binding density functional theory, to develop a better understanding of the electrochemical properties of nanoclusters composed of Ni-based materials and to study the features of polymer membranes used in alkaline fuel cells.
Please see the Ni Electro Can website for additional details.
Molecular dynamics (MD) uses Newton’s equations to simulate the motion of the atoms in a chemical system. To model reactions, the forces must be obtained with quantum chemical (QC) methods as in first-principles MD (FPMD). QC methods are computationally intensive, limiting the use of FPMD to systems containing a few hundred atoms studied on sub-nanosecond time-scales. Meaningful stress rates, which are important for studies of sliding contacts, require the ability to model actual long times. The accessible size and time-scales can be extended if the forces are derived from force-fields (FFs); however, FFs are generally unable to describe reactions. To address these issues we have built on reactive MD methods that switch between FFs during simulations by developing temporal QM/MM methods that use QC forces when reactions occur and FFs otherwise. The rationale is that QC methods are only needed when bonds change, which occurs during only a portion (much less that 1%) of a typical MD simulation. During the rest of the simulation, the bonding is constant and FFs can be used. We have shown that temporal QM/MM can access time-scales several orders of magnitude longer than those accessible with FPMD and reproduces experimental behaviour. We have also developed a means of mitigating the impact of switching potentials on the dynamics of the system.
Present work in this area is focuses on developing metrics that permit the identification of behavior that indicates the onset of chemical reaction when the system is being with an FF that is not designed to allow molecules to react. In addition, we are extending htis method by combining spatial and temporal QM/MM methods to extend the time and size scales that are accessible in MD simulations of reactions.
The accuracy of density functional theory (DFT) calculations depends on the ability of the exchange-correlation (XC) functional to describe inter-electron interactions. A proper description of exchange is important in this context and most modern XC functionals include some degree of exact exchange (EE). The non-local nature exchange operator makes evaluating EE computationally demanding in periodic DFT calculations that use planewave basis sets. Methods for reducing this expense often limit the number of orbital pairs included when evaluating EE by only evaluating EE using pairs of localized states within a certain distance of one another or truncating the Coulomb operator. We have developed a method for calculating EE in periodic systems that uses non-orthogonal generalized Wannier functions (NGWFs) as basis functions. The NGWFs are Fourier series representations of atom-centered basis functions. Unlike conventional planewave calculations, where each planewave is assigned a variational parameter, the Fourier coefficients defining the NGWFs are fixed and each NGWF is assigned a variational coefficient. This approach drastically reduces the number of variational parameters and permits the use of efficient direct diagonalization methods. Tests show the NGWF method is orders of magnitude faster than conventional methods for calculating EE in periodic systems and yields results of similar accuracy. We have recently improved the NGWF method to achieve linear scaling without truncating operators or neglecting integrals.
Ongoing efforts in this area include improving the performance of this method, extending the abilities of the NGWF calculations to permit geometry optimizations, frequency calculations and dynamic correlation via perturbation theory, and ultimately developing and NGWF code that can be distributed for general use among computational chemists.
2014: Gurpaul Kochhar. Skinner Prize, RSC Faraday Discussion
2014: Gurpaul Kochhar. Ontario Graduate Scholarship
2014: Stephanie Whyte. Best Poster Presentation, Canadian Society for Chemistry Conference and Exhibition
2013: Gurpaul Kochhar. R.S. McLaughlin Fellowship
2012-14: Carolyn Carkner. NSERC Industrial Postgraduate Fellowship (Xerox)
2011: Gurpaul Kochhar. The McAdie Doctoral Student Award
2009: Gurpaul Kochhar. Sun Microsystems of Canada HPCVL Scholarship
2009-2014: Nick Mosey. Ontario Ministy of Innovation Early Researcher Award
2009: Nick Mosey. OCGS John Charles Polanyi Prize
2007: Nick Mosey. NSERC Doctoral Prize (top Canadian Ph.D. thesis in the natural sciences)
2006: Nick Mosey. NSERC Howard Alper Postdoctoral Prize (top NSERC PDF applicant across all disciplines of science and engineering)
2006-2008: Nick Mosey. NSERC Postdoctoral Fellowship
2006: Nick Mosey. Paul de Mayo Award (Top Ph.D. thesis in the Department of Chemistry at the University of Western Ontario)