Editorial pubs.acs.org/CR
Introduction: Calculations on Large Systems ranging from force fields to semiempirical approaches to DFT for excited states. The latter includes both time-dependent DFT (TDDFT) and ΔSCF methods. Energy transfer and nonadiabatic effects are also discussed. Importantly, these authors demonstrate the importance of theory as a full synergistic partner of experiments. Evans et al. discuss a very different approach to the study of very large systems, that of kinetic Monte Carlo simulations and coarse-grained mesoscale descriptions for nonequilibrium systems. These authors describe one-dimensional nanoporous systems and two-dimensional surface systems. Of particular interest are catalytic reaction-diffusion systems, spatially discrete stochastic models, first order conversion reactions in linear nanopores, modeling of catalytic reactions on 2-D metal surfaces, and CO oxidation on metal surfaces. Theoretical challenges for treating such systems are discussed. The paper by Odoh, Cramer, Truhlar, and Gagliardi focuses on theoretical treatments of metal organic frameworks (MOFs), including the quantum chemical characterization of properties and reactivities of MOFs. Current and potential uses of MOFs are described, as well as their design and characterization. A summary of electronic structure methods that are used effectively for the study of MOFs is presented, as is a discussion of the connection between molecular and largescale simulations. The creation and requirements of databases for MOFs is discussed. Aikens and co-workers focus on quantum mechanical studies of large metal, metal oxide, and metal chalcogenide nanoparticles and clusters. Clusters of noble metals, as well as transition metal and main group clusters, are considered. The advantages and weaknesses of DFT functionals for these systems are analyzed. Brunk and Rothlisberger discuss QM/MM molecular dynamics simulations of biological systems in ground and electronically excited states. A novel aspect of this paper is an analysis of combining computational systems biology (graph theory and linear optimization) with more traditional QM/MM approaches as a strategy for addressing large biomolecular systems. So, where do we go from here? Fragmentation and embedding methods can significantly reduce the computer resources (time, memory, and disk) that are needed for a calculation, while often retaining remarkable accuracy. Many methods that are discussed in this issue can approach linear scaling. However, such methods are generally limited by the size of the largest fragment, which in turn is often dictated by the degree of delocalization in the system. Fragmentation methods do not do well if one tries to fragment a system across significant delocalization. It is very difficult, for example, to use fragmentation methods for a system such as graphene or a conducting metal. Semiempirical approaches can be used for highly delocalized systems, but these methods frequently do
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n important challenge for electronic structure theory is to develop methods that can treat large molecular species with sufficient accuracy. The very definition of “accuracy” is open to debate, since what one means by accuracy depends on the expectations for the calculations. The focus of this thematic issue of Chemical Reviews is on methods for large molecular systems and their applications to a broad array of problems, including both equilibrium and nonequilibrium problems, and statics and dynamics in both ground and electronically excited states. A full range of methods is discussed, as are their advantages and limitations. The types of systems that are considered herein range from metal clusters to mesoscale 1-D and 2-D systems and every type of problem in between. Collins and Bettens discuss energy-based molecular fragmentation methods. They consider the scaling problem for quantum mechanics (QM) calculations, as well as hybrid QM/molecular mechanic (MM) approaches, with applications to molecular vibrations, nuclear magnetic resonance (NMR), crystal structures, chemical reactions, and reaction dynamics. They address the accuracy issue as it pertains to equilibrium properties, barrier heights, and on-the-fly Monte Carlo simulations and chemical dynamics. Raghavachari and Saha present an analysis of accurate composite and fragment-based models for large molecules. Their discussion includes error cancellation strategies, a survey of fragmentation methods, multilevel QM/QM approaches, electrostatic embedding, hybrid many body methods, overlapping many body methods, and an analysis and comparison of a variety of methods. Morokuma and co-workers discuss the ONIOM method and its applications to a wide variety of problems in ground and excited electronic states in main group and transition metal compounds and processes, and nanomaterials. Akimov and Prezhdo consider the limitations of wave function theory (WFT) and density functional theory (DFT), in the context of both physically motivated approximations and computationally motivated approximations. The diversity of methods discussed in this paper includes as well semiempirical approaches and force fields. The importance of continuing software development is stressed. Wesolowski, Shedge, and Zhou discuss strategies for frozen density embedding theory (FDET) for multilevel simulations of electronic structure. A discourse on the fundamentals of FDET theory is followed by consideration of extensions to the investigation of excited electronic states and by considerations that are important for coupled chromophores. Approximations for multilevel simulations are presented, as are approaches for numerical simulations, including solvatochromism, chromophores in biological environments, induced circular dichroism, NMR, and electron spin resonance (ESR). Kilina, Kilin, and Tretiak focus on light-driven and phononassisted dynamics in organic and semiconductor nanostructures, with particular emphasis on the electronic properties of functionalized quantum dots, nanotubes, and conjugated polymers. They analyze the applicability of various methods, © 2015 American Chemical Society
Special Issue: Calculations on Large Systems Published: June 24, 2015 5605
DOI: 10.1021/acs.chemrev.5b00285 Chem. Rev. 2015, 115, 5605−5606
Chemical Reviews
Editorial
not have sufficient accuracy. Clearly, new approaches are needed that are applicable to the many important highly delocalized species. Such approaches might include the development of novel algorithms for existing ab initio methods, highly parallel algorithms that can take advantage of many thousands or even millions of computer cores, and the use of coprocessors that have garnered considerable attention in recent years. The future for the application of electronic structure theory to large molecular systems is very bright.
Mark S. Gordon* Iowa State University
Lyudmila V. Slipchenko* Purdue University Lyudmila V. Slipchenko is an Associate Professor in the Department of Chemistry at Purdue University. She received her B.S. and M.S. in Applied Mathematics and Physics from Moscow Institute of Physics and Technology and a Ph.D. in Chemistry from the University of Southern California, working in the group of Prof. Anna I. Krylov. As a postdoctoral research associate, she worked with Mark S. Gordon at Iowa State University. Her research focuses on the study of electronic structure, electronic excited states, and noncovalent interactions in the condensed phases.
AUTHOR INFORMATION Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS. Biographies
Mark Gordon, Frances M. Craig Distinguished Professor of Chemistry at Iowa State University and Director of the Ames Laboratory Applied Mathematical and Computational Sciences program, was born and raised in New York City. After completing his B.S. in Chemistry in 1963, Professor Gordon entered the graduate program at Carnegie Institute of Technology, where he received his Ph.D. in 1967 under the guidance of Professor John Pople, 1998 Chemistry Nobel Laureate. Following a postdoctoral research appointment with Professor Klaus Ruedenberg at Iowa State University, Professor Gordon accepted a faculty appointment at North Dakota State University in 1970, where he rose through the ranks, eventually becoming distinguished professor and department chair. He moved to Iowa State University and Ames Laboratory in 1992. Professor Gordon’s research interests are very broadly based in electronic structure theory and related fields, including solvent effects, the theory of liquids, surface science, the design of new materials, and chemical reaction mechanisms. He has authored more than 500 research papers and is a member of the International Academy of Quantum Molecular Science. He received the 2009 American Chemical Society Award for Computers in Chemical and Pharmaceutical Research, and he is a Fellow of the American Physical Society and the American Association for the Advancement of Science. In 2009 he was elected to the inaugural class of the American Chemical Society Fellows. 5606
DOI: 10.1021/acs.chemrev.5b00285 Chem. Rev. 2015, 115, 5605−5606
