Parameter Calibration of Transition-Metal Elements for the Spin-Polarized Self-Consistent-Charge Density-Functional Tight-Binding (DFTB) Method:  Sc, Ti, Fe, Co, and Ni

Zheng, Gaige; Witek, Henryk A.; Bobadova‐Parvanova, Petia; Irle, Stephan; Musaev, Djamaladdin G.; Prabhakar, Rajeev; Morokuma, Keiji; Lundberg, Marcus; Elstner, Marcus; Köhler, Christof; Frauenheim, Thomas

doi:10.1021/ct600312f

Cited by 221 publications

(244 citation statements)

References 70 publications

(135 reference statements)

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“…Instead, we employed self-consistent charge density functional tight binding (SCC-DFTB) calculations to calculate potential energies and forces for the catalytic system, using standard parameterizations. [73][74][75] We note that previous BHMC simulations have confirmed that this computational approach is capable of describing the main intermediates in the catalytic cycle to be studied here. 52 The calculation details for the description of the catalytic hydroformylation process were generally the same as described above; minor changes to the atomic pair cuto↵ distances in Table I were introduced such that optimised molecular structures at the DFTB level gave the correct corresponding molecular graphs in our simulations, and values for the new parameters associated with cobalt were derived in a similar manner.…”

Section: B Catalytic Hydroformylation Of Ethenesupporting

confidence: 71%

Sampling reactive pathways with random walks in chemical space: Applications to molecular dissociation and catalysis

Habershon

2015

The Journal of Chemical Physics

124

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Automatically generating chemical reaction pathways is a significant computational challenge, particularly in the case where a given chemical system can exhibit multiple reactants and products, as well as multiple pathways connecting these. Here, we outline a computational approach to allow automated sampling of chemical reaction pathways, including sampling of di↵erent chemical species at the reaction end-points. The key features of this scheme are (i) introduction of a Hamiltonian which describes a reaction "string" connecting reactant and products, (ii) definition of reactant and product species as chemical connectivity graphs, and (iii) development of a scheme for updating the chemical graphs associated with the reaction end-points. By performing molecular dynamics sampling of the Hamiltonian describing the complete reaction pathway, we are able to sample multiple di↵erent paths in configuration space between given chemical products; by periodically modifying the connectivity graphs describing the chemical identities of the end-points we are also able to sample the allowed chemical space of the system. Overall, this scheme therefore provides a route to automated generation of a "roadmap" describing chemical reactivity. This approach is first applied to model dissociation pathways in formaldehyde, H 2 CO, as described by a parameterised potential energy surface (PES). A second application to the HCo(CO) 3 catalyzed hydroformylation of ethene (oxo process), using density functional tight-binding to model the PES, demonstrates that our graph-based approach is capable of sampling the intermediate paths in the commonly accepted catalytic mechanism, as well as several secondary reactions. Further algorithmic improvements are suggested which will pave the way for treating complex multi-step reaction processes in a more e cient manner. C 2015 AIP Publishing LLC. [http://dx

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Section: B Catalytic Hydroformylation Of Ethenesupporting

confidence: 71%

Sampling reactive pathways with random walks in chemical space: Applications to molecular dissociation and catalysis

Habershon

2015

The Journal of Chemical Physics

124

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“…The DFTB method is À approximately two orders of magnitude faster than first principles DFT and therefore enables longer simulations and provides more adequate model systems for nonequilibrium dynamics of nanosized clusters with quantum mechanical treatment of electrons. In addition, metal-carbon parameters for DFTB have recently been developed by the Morokuma group [57]. A Ànite electronic temperature À approach [58,59] ensures the applicability of the DFTB/MD method for nanometer size metal particles with high electronic densities of states around the Fermi level, as it allows the occupancy of each molecular orbital to change smoothly from 2 to 0 depending on its orbital energy.…”

Section: Dftb-based MD Simulationsmentioning

confidence: 99%

Milestones in molecular dynamics simulations of single-walled carbon nanotube formation: A brief critical review

et al. 2009

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We present a brief review of the most important efforts aimed at simulating single-walled carbon nanotube (SWNT) nucleation and growth processes using molecular dynamics (MD) techniques reported in the literature. MD simulations allow the spatio-temporal movement of atoms during nonequilibrium growth to be followed. Thus, it is hoped that a successful MD simulation of the entire SWNT formation process will assist in the design of chirality-speciÀ c SWNT synthesis techniques. We give special consideration to the role of the metal catalyst À particles assumed in standard theories of SWNT formation, and describe the actual metal behavior observed in the reported MD simulations, including our own recent quantum chemical MD simulations. It is concluded that the use of a quantum potential is essential for a qualitatively correct description of the catalytic behavior of the metal cluster, and that carbide formation does not seem to be a necessary requirement for nucleation and growth of SWNTs according to our most recent quantum chemical MD simulations.

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“…Recent work in the development of SCC-DFTB has focused on the pragmatic advancement of the model, and has resulted in new, efficient, and ever-improving methods, 4,[12][13][14] parameters, 9,[15][16][17][18] and computer codes. 2,19,20 The approach we have chosen is quite different, in that we start from an ab initio-like model that reproduces DFT results very well without the use of parameters, and then identify where and quantify by how much the model breaks down when various approximations are introduced.…”

Section: Introductionmentioning

confidence: 99%

Density-functional expansion methods: Generalization of the auxiliary basis

Giese¹,

York²

2011

The Journal of Chemical Physics

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The formulation of density-functional expansion methods is extended to treat the second and higherorder terms involving the response density and spin densities with an arbitrary single-center auxiliary basis. The two-center atomic orbital products are represented by the auxiliary functions centered about those two atoms, and the mapping coefficients are determined from a local constrained variational procedure. This two-center variational procedure allows the mapping coefficients to be pretabulated and splined as a function of internuclear separation for efficient look up. The splines of mapping coefficients have a range no longer than that of the overlap integrals, and the auxiliary density appears as a single point-multipole expansion to all nonoverlapping atoms, thus allowing for the trivial implementation of a linear-scaling algorithm. The method is tested using Gaussian multipole expansions, and the effect of angular and radial completeness is explored. Several auxiliary basis sets are parametrized and compared to an auxiliary basis analogous to that used in the selfconsistent-charge density-functional tight-binding model, and the method is demonstrated to greatly improve the representation of the density response with respect to a reference expansion model that does not use an auxiliary basis.

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Parameter Calibration of Transition-Metal Elements for the Spin-Polarized Self-Consistent-Charge Density-Functional Tight-Binding (DFTB) Method: Sc, Ti, Fe, Co, and Ni

Cited by 221 publications

References 70 publications

Sampling reactive pathways with random walks in chemical space: Applications to molecular dissociation and catalysis

Sampling reactive pathways with random walks in chemical space: Applications to molecular dissociation and catalysis

Milestones in molecular dynamics simulations of single-walled carbon nanotube formation: A brief critical review

Density-functional expansion methods: Generalization of the auxiliary basis

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