Quantum Monte Carlo Study of π-Bonded Transition Metal Organometallics: Neutral and Cationic Vanadium–Benzene and Cobalt–Benzene Half Sandwiches

Horvathova, Lucia; Dubecký, Matúš; Mitáš, Luboš; Štich, Ivan

doi:10.1021/ct300887t

Cited by 22 publications

(32 citation statements)

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“…Previous DFT and WF-based computational studies [30,31,54] have identified the hollow site as being a stable binding site for cobalt on the substrate, although some experimental studies show evidence of binding at the top site as well [55]. Here, we focus on modelling the hollow-site complex because one key aim of this work is to assess the reliability of previous calculations.…”

Section: Interaction Of Cobalt and Benzenementioning

confidence: 99%

“…These systems typically have many neardegenerate states, and may show strong electron-correlation effects. Approximate DFT descriptions of cobalt approaching a graphene model can be strongly functional dependent [29,30], and correlated wavefunction-based methods are probably needed to accurately analyse the energetics of such systems. Although wavefunction-based methods can provide a more consistent description [30,31], the computational costs typically rise very quickly with system size.…”

Section: Introductionmentioning

confidence: 99%

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Computational study of adsorption of cobalt on benzene and coronene

2015

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We investigate the binding of the cobalt atom on small aromatic model systems as a proxy for interaction with graphene, using density functional theory, coupled-cluster theory, and combinations of them using projector-based quantum embedding. We set out in some detail the electronic structure of the cobalt atom alone, because some nuances of atomic structure appear to have been overlooked in previous studies. Two states of the complex in particular are studied: those formed from the a 4 F ground state of the atom; and from c 2 D, the lowest doublet state with configuration 3d 9 4s 0 . We highlight the difficulties in extracting reliable results from typical approximate density functionals, and demonstrate that embedding calculations using the coupled-cluster theory in an active subsystem greatly reduce functional dependence, and produce a picture more consistent with the available experimental information. Our results cast doubt on previous calculations that have predicted strong chemisorptive binding between graphene and the c 2 D state of cobalt.

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Section: Interaction Of Cobalt and Benzenementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Computational study of adsorption of cobalt on benzene and coronene

2015

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“…47,[51][52][53][54] Modern massively parallel computers have expanded the applicability of QMC methods not only to larger molecular systems but also to periodic systems because of their high parallel efficiency. 55,56 One of the most practical QMC methods, fixed-node diffusion Monte Carlo (FN-DMC), has been applied to noncovalent molecular systems and demonstrated to have an accuracy comparable to CCSD(T).…”

Section: Introductionmentioning

confidence: 99%

“…55,56 One of the most practical QMC methods, fixed-node diffusion Monte Carlo (FN-DMC), has been applied to noncovalent molecular systems and demonstrated to have an accuracy comparable to CCSD(T). 47,[51][52][53][54] Since the accuracy of FN-DMC depends critically on the choice of trial nodal surface, one should take care when generating this surface. If one uses DFT, experience shows that the nodal structures generally depend on the functional employed, and many choices are available in the literature.…”

Section: Introductionmentioning

confidence: 99%

Diffusion Monte Carlo Study of Para-Diiodobenzene Polymorphism Revisited

Hongo

Watson

Iitaka

et al. 2015

J. Chem. Theory Comput.

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We revisit our investigation of the diffusion Monte Carlo (DMC) simulation of p-DIB molecular crystal polymorphism. [J. Phys. Chem. Lett. 2010Lett. , 1, 1789Lett. -1794 We perform, for the first time, a rigorous study of finite-size effects and choice of nodal surface on the prediction of polymorph stability in molecular crystals using fixed-node DMC. Our calculations are the largest which are currently feasible using the resources of the K computer and provide insights into the formidable challenge of predicting such properties from first principles. In particular, we show that finite-size effects can influence the trial nodal surface of a small (1×1×1) simulation cell considerably. We therefore repeated our DMC simulations with a 1×3×3 simulation cell, which is the largest such calculation to date. We used a DFT nodal surface generated with the PBE functional and we accumulated statistical samples with ∼ 6.4 × 10 5 core-hours for each polymorph. Our final results predict a polymorph stability consistent with experiment, but indicate that results in our previous paper were somewhat fortuitous.We analyze the finite-size errors using model periodic Coulomb (MPC) interactions and kinetic energy corrections, according to the CCMH scheme of Chiesa, Ceperley, Martin, and Holzmann. We investigate the dependence of the finite-size errors on different aspect ratios of the simulation cell (k-mesh convergence) in order to understand how to choose an appropriate ratio for the DMC calculations. Even in the most expensive simulations currently possible, we show that the finite size errors in the DMC total energies are far larger than the energy difference between the two polymorphs, although error cancellation means that the polymorph prediction is accurate. Finally, we found that the T -move scheme is essential for these massive DMC simulations in order to circumvent population explosions and large time-step biases.

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“…Nonetheless, this possibility is worth investigating, particularly in the light of recent remarkable improvements in the QMC technology and quality of the results that can routinely be obtained (see Refs. [37][38][39][40][41][42][43][44][45][46] for representative examples).…”

Section: Introductionmentioning

confidence: 99%