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Two- and three-body interatomic dispersion energy contributions to binding in molecules and solids ; Tkatchenko, Alexandre in Journal of Chemical Physics (2010), 132(23), We present numerical estimates of the leading two- and three-body dispersion energy terms in van der Waals interactions for a broad variety of molecules and solids. The calculations are based on London ... [more ▼] We present numerical estimates of the leading two- and three-body dispersion energy terms in van der Waals interactions for a broad variety of molecules and solids. The calculations are based on London and Axilrod-Teller-Muto expressions where the required interatomic dispersion energy coefficients, C6 and C9, are computed "on the fly" from the electron density. Inter- and intramolecular energy contributions are obtained using the Tang-Toennies (TT) damping function for short interatomic distances. The TT range parameters are equally extracted on the fly from the electron density using their linear relationship to van der Waals radii. This relationship is empiricially determined for all the combinations of He-Xe rare gas dimers, as well as for the He and Ar trimers. The investigated systems include the S22 database of noncovalent interactions, Ar, benzene and ice crystals, bilayer graphene, C60 dimer, a peptide (Ala10), an intercalated drug-DNA model [ellipticine- d (CG) 2], 42 DNA base pairs, a protein (DHFR, 2616 atoms), double stranded DNA (1905 atoms), and 12 molecular crystal polymorphs from crystal structure prediction blind test studies. The two- and three-body interatomic dispersion energies are found to contribute significantly to binding and cohesive energies, for bilayer graphene the latter reaches 50% of experimentally derived binding energy. These results suggest that interatomic three-body dispersion potentials should be accounted for in atomistic simulations when modeling bulky molecules or condensed phase systems. © 2010 American Institute of Physics. [less ▲] Detailed reference viewed: 202 (1 UL)Van der Waals Interactions Between Organic Adsorbates and at Organic/Inorganic Interfaces Tkatchenko, Alexandre ; ; et al in MRS BULLETIN (2010), 35(6), 435-442 Van der Waals (vdW) interactions play a prominent role in the structure and function of organic/organic and organic/inorganic interfaces. Their accurate determination from first principles, however, is a ... [more ▼] Van der Waals (vdW) interactions play a prominent role in the structure and function of organic/organic and organic/inorganic interfaces. Their accurate determination from first principles, however, is a notoriously difficult task. Recently, a surge of interest in modeling vdW interactions has led to promising theoretical developments. This article reviews the state-of-the-art of describing vdW interactions by density-functional theory with respect to accuracy and practicability. The performance of the different methods is demonstrated for simple systems, such as rare-gas dimers and small organic molecules. The nature of binding at organic/inorganic interfaces is then exemplified for the perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) molecule at surfaces of coinage metals. This fundamental system is the best-characterized organic molecule/metal interface in experiment and theory. We emphasize the crucial importance of a balanced description of both geometry and electronic structure in order to understand and model the properties of such systems. Finally, the relevance of vdW interactions to the function of actual devices based on interfaces is discussed. [less ▲] Detailed reference viewed: 158 (0 UL)Describing both dispersion interactions and electronic structure using density functional theory: The case of metal-phthalocyanine dimers ; Tkatchenko, Alexandre ; et al in Journal of Chemical Theory and Computation (2010), 6(1), 81-90 Noncovalent interactions, of which London dispersion is an important special case, are essential to many fields of chemistry. However, treatment of London dispersion is inherently outside the reach of ... [more ▼] Noncovalent interactions, of which London dispersion is an important special case, are essential to many fields of chemistry. However, treatment of London dispersion is inherently outside the reach of (semi)local approximations to the exchange-correlation functional as well as of conventional hybrid density functionals based on semilocal correlation. Here, we offer an approach that provides a treatment of both dispersive interactions and the electronic structure within a computationally tractable scheme. The approach is based on adding the leading interatomic London dispersion term via pairwise ion-ion interactions to a suitably chosen nonempirical hybrid functional, with the dispersion coefficients and van der Waals radii determined from first-principles using the recently proposed "TS-vdW" scheme (Tkatchenko, A.; Scheffler, M. Phys. Rev. Lett. 2009, 102, 073005). This is demonstrated via the important special case of weakly bound metal-phthalocyanine dimers. The performance of our approach is additionally compared to that of the semiempirical M06 functional. We find that both the PBE-hybrid+vdW functional and the M06 functional predict the electronic structure and the equilibrium geometry well, but with significant differences in the binding energy and in their asymptotic behavior. Copyright © 2010 American Chemical Society. [less ▲] Detailed reference viewed: 157 (0 UL)Stacking and registry effects in layered materials: The case of hexagonal boron nitride ; ; et al in Physical Review Letters (2010), 105(4), The interlayer sliding energy landscape of hexagonal boron nitride (h-BN) is investigated via a van der Waals corrected density functional theory approach. It is found that the main role of the van der ... [more ▼] The interlayer sliding energy landscape of hexagonal boron nitride (h-BN) is investigated via a van der Waals corrected density functional theory approach. It is found that the main role of the van der Waals forces is to anchor the layers at a fixed distance, whereas the electrostatic forces dictate the optimal stacking mode and the interlayer sliding energy. A nearly free-sliding path is identified, along which band gap modulations of ∼0.6eV are obtained. We propose a simple geometric model that quantifies the registry matching between the layers and captures the essence of the corrugated h-BN interlayer energy landscape. The simplicity of this phenomenological model opens the way to the modeling of complex layered structures, such as carbon and boron nitride nanotubes. © 2010 The American Physical Society. [less ▲] Detailed reference viewed: 162 (0 UL)Dispersion-corrected Moller-Plesset second-order perturbation theory Tkatchenko, Alexandre ; ; et al in Journal of Chemical Physics (2009), 131 We show that the often unsatisfactory performance of Møller-Plesset second-order perturbation theory (MP2) for the dispersion interaction between closed-shell molecules can be rectified by adding a ... [more ▼] We show that the often unsatisfactory performance of Møller-Plesset second-order perturbation theory (MP2) for the dispersion interaction between closed-shell molecules can be rectified by adding a correction Δ C n / Rn, to its long-range behavior. The dispersion-corrected MP2 (MP2+ΔvdW) results are in excellent agreement with the quantum chemistry "gold standard" [coupled cluster theory with single, double and perturbative triple excitations, CCSD(T)] for a range of systems bounded by hydrogen bonding, electrostatics and dispersion forces. The MP2+ΔvdW method is only mildly dependent on the short-range damping function and consistently outperforms state-of-the-art dispersion-corrected density-functional theory. © 2009 American Institute of Physics. [less ▲] Detailed reference viewed: 219 (1 UL)Accurate molecular van der Waals interactions from ground-state electron density and free-atom reference data Tkatchenko, Alexandre ; in Physical Review Letters (2009), 102(7), We present a parameter-free method for an accurate determination of long-range van der Waals interactions from mean-field electronic structure calculations. Our method relies on the summation of ... [more ▼] We present a parameter-free method for an accurate determination of long-range van der Waals interactions from mean-field electronic structure calculations. Our method relies on the summation of interatomic C6 coefficients, derived from the electron density of a molecule or solid and accurate reference data for the free atoms. The mean absolute error in the C6 coefficients is 5.5% when compared to accurate experimental values for 1225 intermolecular pairs, irrespective of the employed exchange-correlation functional. We show that the effective atomic C6 coefficients depend strongly on the bonding environment of an atom in a molecule. Finally, we analyze the van der Waals radii and the damping function in the C6R-6 correction method for density-functional theory calculations. © 2009 The American Physical Society. [less ▲] Detailed reference viewed: 243 (4 UL)Popular Kohn-Sham density functionals strongly overestimate many-body interactions in van der Waals systems Tkatchenko, Alexandre ; in Physical Review. B, Condensed Matter and Materials Physics (2008), 78(4), We find spuriously large repulsive many-body contributions to binding energies of rare gas systems for the first three rungs of "Jacob's Ladder" within Kohn-Sham density functional theory. While the ... [more ▼] We find spuriously large repulsive many-body contributions to binding energies of rare gas systems for the first three rungs of "Jacob's Ladder" within Kohn-Sham density functional theory. While the description of van der Waals dimers is consistently improved by the pairwise London C6 / R6 correction, inclusion of a corresponding three-body Axilrod-Teller C9 / R9 term only increases the repulsive error. Our conclusions based on extensive solid state and molecular electronic structure calculations are particularly relevant for condensed phase van der Waals systems. © 2008 The American Physical Society. [less ▲] Detailed reference viewed: 166 (1 UL)On the accuracy of density-functional theory exchange-correlation functionals for H bonds in small water clusters. II. the water hexamer and van der Waals interactions ; ; et al in Journal of Chemical Physics (2008), 129(19), Second order Møller-Plesset perturbation theory at the complete basis set limit and diffusion quantum Monte Carlo are used to examine several low energy isomers of the water hexamer. Both approaches ... [more ▼] Second order Møller-Plesset perturbation theory at the complete basis set limit and diffusion quantum Monte Carlo are used to examine several low energy isomers of the water hexamer. Both approaches predict the so-called prism to be the lowest energy isomer, followed by cage, book, and cyclic isomers. The energies of the four isomers are very similar, all being within 10-15 meV/ H2 O. These reference data are then used to evaluate the performance of several density-functional theory exchange-correlation (xc) functionals. A subset of the xc functionals tested for smaller water clusters [I. Santra, J. Chem. Phys. 127, 184104 (2007)] has been considered. While certain functionals do a reasonable job at predicting the absolute dissociation energies of the various isomers (coming within 10-20 meV/ H2 O), none predict the correct energetic ordering of the four isomers nor does any predict the correct low total energy isomer. All xc functionals tested either predict the book or cyclic isomers to have the largest dissociation energies. A many-body decomposition of the total interaction energies within the hexamers leads to the conclusion that the failure lies in the poor description of van der Waals (dispersion) forces in the xc functionals considered. It is shown that the addition of an empirical pairwise (attractive) C6 R-6 correction to certain functionals allows for an improved energetic ordering of the hexamers. The relevance of these results to density-functional simulations of liquid water is also briefly discussed. © 2008 American Institute of Physics. [less ▲] Detailed reference viewed: 179 (0 UL)Comprehensive study of the potential energy surface minima of a monolayer on (111) surface Tkatchenko, Alexandre in Physical Review. B, Condensed Matter and Materials Physics (2007), 75(8), The potential energy landscape of a monolayer adsorbed on well-ordered (111) surface is analyzed for periodic cells with a variable number of adsorbate (Nads) and substrate (Nsub) particles. The atom ... [more ▼] The potential energy landscape of a monolayer adsorbed on well-ordered (111) surface is analyzed for periodic cells with a variable number of adsorbate (Nads) and substrate (Nsub) particles. The atom-surface potential is described by the first Fourier series term with variable corrugation, while the lateral interaction in the monolayer is modeled by a repulsive exponential term. Special attention is devoted to the determination of the total number of minima for given Nads and Nsub and the probability of relaxation to the global minimum in each of the unit cells, as well as the construction of the lowest energy versus coverage curve as a function of the atom-surface potential corrugation. We find that the global appearance of the energy landscape in the majority of the unit cells is particularly simple, characterized by the global minimum positioned in a very wide basin and the high-energy minima forming a tail structure. However, this rule is broken for several unit cells when the corrugation of the atom-surface potential becomes large, making the location of the global minimum a rather difficult task. Despite the simplicity of our model, phase transitions from commensurate to striped incommensurate to hexagonal incommensurate rotated structures are observed. © 2007 The American Physical Society. [less ▲] Detailed reference viewed: 162 (1 UL)Commensurate monolayers on surfaces: Geometry and ground states Tkatchenko, Alexandre in Physical Review. B, Condensed Matter and Materials Physics (2007), 75(23), We present a procedure for the generation of all rigid commensurate monolayer-surface structures of a given symmetry, up to a certain number of adsorbate particles, Nads, in the unit cell. It is shown ... [more ▼] We present a procedure for the generation of all rigid commensurate monolayer-surface structures of a given symmetry, up to a certain number of adsorbate particles, Nads, in the unit cell. It is shown that the minimum energy structures in each unit cell are related to a well-defined sequence of Fourier terms of the single-particle-surface potential. This fact allows the prediction of stable commensurate monolayer-surface structures with the only knowledge of Fourier coefficients of the atom-surface potential. The impact of the presented theory for theoretical and experimental determination of atomic and molecular monolayer ground states, as well as its extension to higher dimensions (i.e., for intercalated crystals), is discussed. © 2007 The American Physical Society. [less ▲] Detailed reference viewed: 172 (1 UL)Potential energy landscape of monolayer-surface systems governed by repulsive lateral interactions: The case of (3 x 3)-I-Pt(111) Tkatchenko, Alexandre ; ; in PHYSICAL REVIEW LETTERS (2006), 97(3), Combined density functional theory (DFT) and Monte Carlo (MC) approach is applied to study the potential energy landscape of four iodine atoms adsorbed on the Pt(111) surface in a (3x3) unit cell. Three ... [more ▼] Combined density functional theory (DFT) and Monte Carlo (MC) approach is applied to study the potential energy landscape of four iodine atoms adsorbed on the Pt(111) surface in a (3x3) unit cell. Three critical points were identified: (3x3)-sym and (3x3)-asym, corresponding to structures well known from experimental studies, while the third one (3x3)-zigzag is a new structure not reported before. An interaction model fitted to DFT calculations allows us to explain the difference between arrangements of iodine monolayer in vacuum, air, and solution environments as a result of different repulsion regimes. [less ▲] Detailed reference viewed: 148 (2 UL)Adsorption of Ar on graphite using London dispersion forces corrected Kohn-Sham density functional theory Tkatchenko, Alexandre ; in Physical Review. B (2006), 73(15), Using Kohn-Sham (KS) density functional theory, the adsorption of Ar on graphite has been computed with various conventional exchange-correlation functionals. While the local density approximation yields ... [more ▼] Using Kohn-Sham (KS) density functional theory, the adsorption of Ar on graphite has been computed with various conventional exchange-correlation functionals. While the local density approximation yields a reasonable estimate of equilibrium distance and energy, three generalized gradient approximated functionals fail. Extending the KS Hamiltonian by an empirical nonlocal and atom-centered potential enables quantitative predictions. The adsorption on the on-top, hollow, and bridge sites has been investigated, and it is found that the London dispersion corrected calculations prefer the hollow site which is in agreement with other studies. Furthermore, the adsorption effect of several submonolayer coverages and of the graphitic bulk has been studied. [less ▲] Detailed reference viewed: 195 (2 UL)Role of high-order Fourier terms for stability of monolayer-surface structures: Numerical simulations Tkatchenko, Alexandre in Physical Review. B, Condensed Matter and Materials Physics (2006), 74(23), The role of high-order atom-surface Fourier terms is analyzed for the monolayer with coverage θ= 3 7 on (111) surface in cells with variable number of adsorbate atoms, allowed to relax to obtain the ... [more ▼] The role of high-order atom-surface Fourier terms is analyzed for the monolayer with coverage θ= 3 7 on (111) surface in cells with variable number of adsorbate atoms, allowed to relax to obtain the global minimum in each of the unit cells. A Fourier expansion with one or two shells of reciprocal cell vectors is used and three different models for the lateral interactions in the monolayer are tested, from purely repulsive to a real HFD-B2 potential. It is found that the simple commensurate (7x7) R19.1° three-atom structure is the most stable only when the contribution of the second Fourier term is included. In contrast to the conventional view, higher corrugation of the single-term Fourier model favors incommensurability. Evidence is collected that the high-order Fourier terms are mandatory for the stabilization of commensurate structures of an infinite monolayer. © 2006 The American Physical Society. [less ▲] Detailed reference viewed: 157 (3 UL)Classification of hexagonal adlayer arrangements by means of collective geometrical properties Tkatchenko, Alexandre ; in Journal of Chemical Physics (2006), 125(16), Unequal-sphere packing model is applied for the simulation of large number of hexagonal adlayer structures with surface coverage between θ= 1 3 and θ=1 on the hexagonal substrate, with atomic radius of ... [more ▼] Unequal-sphere packing model is applied for the simulation of large number of hexagonal adlayer structures with surface coverage between θ= 1 3 and θ=1 on the hexagonal substrate, with atomic radius of the adsorbate and substrate atoms as the only input. Each structure is characterized with respect to collective adlayer properties: the average adlayer height and the adlayer roughness. The distribution of hexagonal arrangements is presented in a special plot, which can be used for identification and characterization of hexagonal adlayers of different surface coverages and atomic registries. The most likely structures are related to the extreme values of our model parameters. The usefulness of this methodology is successfully demonstrated by comparison with some real adsorbate-substrate systems, i.e., halogens and rare gases adsorbed on (111) surface. Besides the agreement with experimental results, our model offers new insight into the formation of atomic adlayers and detailed analysis of the atomic registry. We believe that our approach will be of use for identification of probable structures among the large number of combinatorial possibilities in theoretical studies and for better interpretation of experimental results (i.e., scanning-tunneling microscopy images of atomic adlayers). © 2006 American Institute of Physics. [less ▲] Detailed reference viewed: 153 (0 UL)Analytic theory of hexagonal monolayer interacting with hexagonal substrate Tkatchenko, Alexandre in Physical Review. B (2006), 74(3), Analytic theory of the infinite rigid hexagonal monolayer interacting with hexagonal substrate is developed. The interaction potential is described by a Fourier series with up to six shells of the ... [more ▼] Analytic theory of the infinite rigid hexagonal monolayer interacting with hexagonal substrate is developed. The interaction potential is described by a Fourier series with up to six shells of the reciprocal cell vectors. It is rigorously shown that energy of minimum structures is directly related to their symmetry, assuming a decaying behavior of Fourier coefficients. Preliminary comparison with real systems of halogens and alkalis adsorbed on metal surfaces is encouraging and indicates that the adsorbate-substrate interaction is one of the main driving forces in the monolayer formation. The need of detailed ab initio calculations to obtain the Fourier coefficients for different complex adsorption systems is emphasized. Our results indicate the importance of accurate description of the adsorbate-substrate interactions for quantitative theory of monolayer epitaxy on well-ordered surfaces. [less ▲] Detailed reference viewed: 176 (3 UL)Unequal-sphere packing model for simulation of the uniaxially compressed iodine adlayer on Au(111) Tkatchenko, Alexandre ; in JOURNAL OF PHYSICAL CHEMISTRY B (2005), 109(46), 21710-21715 A simple unequal-sphere packing (USP) model, based on pure geometrical principles, was applied to study the centered-rectangular iodine c(p x root 3)R30 degrees adlayer on the Au(111) surface, well-known ... [more ▼] A simple unequal-sphere packing (USP) model, based on pure geometrical principles, was applied to study the centered-rectangular iodine c(p x root 3)R30 degrees adlayer on the Au(111) surface, well-known from surface X-ray structure (SXS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) experiments. To reproduce the exact patterns observed in experiments, two selective conditions-minimum average adsorbate height and minimum adlayer roughness-were imposed. As a result, a series of adlayer patterns with c(p x root 3)R30 degrees symmetry (2.3 < p < 3), with precise structural details, including atomic registry and identification of the p-bisector as the most likely trajectory for the iodine adatom movement during the so-called uniaxial compression phenomenon, were identified. In addition, using the same model, the difference between the iodine adlayer arranged in hexagonal and centered-rectangular c(p x root 3)R30 degrees patterns, as in the case of Pt(111) and Au(111) surfaces, was investigated. Qualitative and quantitative comparison shows that iodine adatoms in these two arrangements differ significantly in atomic registry, distance from the substrate, and the adlayer corrugation. Our findings could be of special interest in the study of the nature of the iodine adatom bonding to different substrates (i.e., Au vs Pt). [less ▲] Detailed reference viewed: 149 (1 UL)Detailed characterization of (3X3) iodine adlayer on Pt(111) by unequal-sphere packing model Tkatchenko, Alexandre ; in JOURNAL OF CHEMICAL PHYSICS (2005), 122(9), A simple unequal-sphere packing model is applied to study the iodine (3x3) adlayer on the Pt(111) surface. By using a newly introduced parameter, defined as the average adsorbate height, three ... [more ▼] A simple unequal-sphere packing model is applied to study the iodine (3x3) adlayer on the Pt(111) surface. By using a newly introduced parameter, defined as the average adsorbate height, three characteristic adlattices, (3x3)-sym, (3x3)-asym, and (3x3)-lin, have been selected and characterized in great detail, including the exact adatom registry. The (3x3)-sym iodine adlattice, observed in many experimental studies appears to be, on average, the closest one to the substrate surface. A special contour plot of average adsorbate height vs X and Y positions of the (3x3) iodine unit cell indicates the existence of two local minima which are related to preferential formation of (3x3)-sym and (3x3)-asym iodine adlattices. Our model gives good agreement with experimental findings, and explains the mechanism of preferential appearance of (3x3)-sym and (3x3)-asym structures. (C) 2005 American Institute of Physics. [less ▲] Detailed reference viewed: 168 (2 UL)Unequal-sphere packing model for the structural arrangement of the well-ordered adsorbate-substrate system Tkatchenko, Alexandre ; in Physical Review. B, Condensed Matter and Materials Physics (2004), 70(19), 1-8 In order to understand the well-ordered adsorbate-substrate systems at atomic level, a method is developed based on the simulation of packing arrangements for layers of unequal spheres, in three ... [more ▼] In order to understand the well-ordered adsorbate-substrate systems at atomic level, a method is developed based on the simulation of packing arrangements for layers of unequal spheres, in three-dimensional space. The model, based on geometrical principles, is developed for fee structure consisting of two hexagonal ordered layers. During simulation, adsorbate spheres were accommodated in different positions, forming a great variety of structures, in dependence of the intersphere distance of the upper layer spheres. Using the average height of the adsorbate layer on the flat substrate as a determinant parameter, several specific structures have been selected as the most probable: (√3 x √3)R30°, (√7 x √7)R19.1°, and (3 x 3). Indeed, they correspond to typical accommodations of the iodine adatoms on the Pt(111) surface, earlier found in experimental studies, which clearly supports the validity of our model. The model developed in our study could completely and satisfactorily describe the accommodation process of the iodine adlayer on the Pt(111) surface. This methodology could be of great help for interpretation of scanning tunneling microscopy images, better understanding of adlayer structures, and design of adsorbate-substrate systems with exciting properties. [less ▲] Detailed reference viewed: 267 (9 UL) |
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