Unified treatment of asymptotic van der Waals forces

Hult, Erika; Rydberg, Henrik; Lundqvist, Bengt I.; Langreth, David C.

doi:10.1103/physrevb.59.4708

Cited by 94 publications

(90 citation statements)

References 42 publications

(26 reference statements)

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“…It is well-known that the dispersion interactions can not be represented accurately by a local or a semilocal exchange-correlation functional, such as that provided by the commonly used LDA and GGA functionals. 73 We have therefore decided not to include the dispersion parameters in the fitting procedure, but rather to fix them to some given values. The choice of these values is discussed in the next section.…”

Section: Obtaining the Parameters From Force-matching And Multipmentioning

confidence: 99%

Including many-body effects in models for ionic liquids

Salanne¹,

Rotenberg²,

Jahn³

et al. 2012

Theor Chem Acc

126

118

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Realistic modeling of ionic systems necessitates taking explicitly account of many-body effects. In molecular dynamics simulations, it is possible to introduce explicitly these effects through the use of additional degrees of freedom. Here we present two models: The first one only includes dipole polarization effect, while the second also accounts for quadrupole polarization as well as the effects of compression and deformation of an ion by its immediate coordination environment. All the parameters involved in these models are extracted from first-principles density functional theory calculations. This step is routinely done through an extended force-matching procedure, which has proven to be very succesfull for molten oxides and molten fluorides. Recent developments based on the use of localized orbitals can be used to complement the force-matching procedure by allowing for the direct calculations of several parameters such as the individual polarizabilities.

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Section: Obtaining the Parameters From Force-matching And Multipmentioning

confidence: 99%

Including many-body effects in models for ionic liquids

Salanne¹,

Rotenberg²,

Jahn³

et al. 2012

Theor Chem Acc

126

118

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“…While the LDA (and GGA also) yields by construction correct results for a system with uniform electron distribution, these approximations can not capture longrange vdW interaction in systems with sparse electron distribution and several challenges to incorporate vdW interaction in the DFT have been made. [21][22][23][24][25][26][27][28][29] Rydberg et al have actually devised a tractable scheme for planar geometry 30 and applied it to graphite and other materials of layered structure. 20,31 Their calculations for graphite have provided an improvement over the LDA and GGA results in that the interlayer binding energy as a function of the interlayer separation shows a desired behavior expected from the presence of vdW interaction.…”

Section: Introductionmentioning

confidence: 99%

Semiempirical approach to the energetics of interlayer binding in graphite

2004

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The interlayer binding energy of graphite is obtained by a semiempirical method in which ab initio calculations based on the density functional theory (DFT) are supplemented with an empirical van der Waals (vdW) interaction. The local density approximation (LDA) and generalized gradient approximation (GGA) are used in the DFT calculations, and the damping (or interpolation) function used to combine these DFT results with an empirical vdW interaction is fitted to the observed interlayer spacing and c-axis elastic constant. The interlayer binding energies calculated in the LDA and GGA are quite different, but the combined results are nearly the same, which may be a necessary condition and provide reinforcements for validating the method. The present results are also consistent with those obtained by the empirical method based on the Lennard-Jones potential, and both are in reasonable agreement with the recent experimental data. These results indicate that, in contrast to the prevailing belief, the LDA underestimates the interlayer binding energy of graphite.

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“…Here we show that the recently proposed density functional [5] with nonlocal correlations, E nl c [n], gives separations, binding energies, and compressibilities of these layered systems in fair agreement with experiment. This planar case bears on the development of vdW density functionals for general geometries [6,7], as do asymptotic vdW functionals [8].Figure 1 with its 'inner surfaces' defines the problem: voids of ultra-low density, across which electrodynamics leads to vdW coupling. This coupling depends on the polarization properties of the layers themselves, and not on small regions of density overlap between the layers, excluding proper account in LDA or GGA.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Van der Waals Density Functional for Layered Structures

Rydberg

Dion²,

Jacobson³

et al. 2003

Phys. Rev. Lett.

659

645

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To understand sparse systems we must account for both strong local atom bonds and weak nonlocal van der Waals forces between atoms separated by empty space. A fully nonlocal functional form [H. Rydberg, B.I. Lundqvist, D.C. Langreth, and M. Dion, Phys. Rev. B 62, 6997 (2000)] of density-functional theory (DFT) is applied here to the layered systems graphite, boron nitride, and molybdenum sulfide to compute bond lengths, binding energies, and compressibilities. These key examples show that the DFT with the generalized-gradient approximation does not apply for calculating properties of sparse matter, while use of the fully nonlocal version appears to be one way to proceed.PACS numbers: 71.15. Mb, 61.50.Lt, 31.15.Ew, Calculations of structure and other properties of sparse systems must account for both strong local atom bonds and weak nonlocal van der Waals (vdW) forces between atoms separated by empty space. Present methods are unable to describe the true interactions of sparse systems, abundant among materials and molecules. Key systems, like graphite, BN, and MoS 2 , have layered structures. While today's standard tool, density-functional theory (DFT), has broad application, the common local (LDA) and semilocal density approximations (GGA) [1,2,3,4] for exchange and correlation, E xc [n], fail to describe the interactions at sparse electron densities. Here we show that the recently proposed density functional [5] with nonlocal correlations, E nl c [n], gives separations, binding energies, and compressibilities of these layered systems in fair agreement with experiment. This planar case bears on the development of vdW density functionals for general geometries [6,7], as do asymptotic vdW functionals [8].Figure 1 with its 'inner surfaces' defines the problem: voids of ultra-low density, across which electrodynamics leads to vdW coupling. This coupling depends on the polarization properties of the layers themselves, and not on small regions of density overlap between the layers, excluding proper account in LDA or GGA. For large interplanar separation d the vdW interaction energy between planes behaves as −c 4 /d 4 , while LDA or GGA necessarily predicts an exponential falloff. Layers rolled up to form two (i) nanotubes with parallel axes a distance l apart interact as −c 5 /l 5 , or (ii) balls (e.g., C 60 ), a distance r apart, as −c 6 /r 6 . If by fluke an LDA or GGA were to give the correct equilibrium for one shape, it would necessarily fail for the others. The simple expedient of adding the standard asymptotic vdW energies as corrections to the correlation energy of LDA or GGA also fails. The true vdW interaction between two close sheets must be (i) substantially stronger (Fig. 1), (ii) seamless, and (iii) saturate as d shrinks (Fig. 2).Like earlier work directly calculating nonlocal correlations between two jellium slabs [9], the vdW density functional (vdW-DF) theory [5] used here exploits assumed planar symmetry. It divides the correlation energy functional into two pieces,, where E nl c [n] is defined to in...

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Unified treatment of asymptotic van der Waals forces

Cited by 94 publications

References 42 publications

Including many-body effects in models for ionic liquids

Including many-body effects in models for ionic liquids

Semiempirical approach to the energetics of interlayer binding in graphite

Van der Waals Density Functional for Layered Structures

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