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Van der Waals density functional from multipole dispersion interactions

Neemias Alves de Lima

Citation: The Journal of Chemical Physics 132, 014110 (2010); doi: 10.1063/1.3282265 View online: http://dx.doi.org/10.1063/1.3282265

View Table of Contents: http://aip.scitation.org/toc/jcp/132/1 Published by the American Institute of Physics

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Van der Waals density functional from multipole dispersion interactions

Neemias Alves de Limaa兲

Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, Caixa Postal 1524, CEP 59072–970 Natal, RN, Brazil

共Received 17 August 2009; accepted 9 December 2009; published online 6 January 2010; publisher error corrected 7 January 2010兲

We present a van der Waals density functional from high order multipole dispersion interactions between pairs of atoms. Calculated C2mⱕ16 dispersion coefficients for dimers involving alkali, alkaline-earth, and noble gas atoms show mean absolute deviations in the range of 2%–6% from highly accurate calculations. This successful test indicates that this approach can yield efficient algorithms for calculation of van der Waals forces. © 2010 American Institute of Physics. 关doi:10.1063/1.3282265兴

Although, in principle, density functional theory共DFT兲1 within the Kohn–Sham scheme2is able to provide the exact ground state energy of an electronic system, present local and semilocal density functional approximations关local spin-density approximation, generalized gradient approximation 共GGA兲, and meta-GGA兴3

are inappropriate to describe long-range electron correlation and consequently fail for disper-sion or van der Waals 共vdW兲 interactions.4This problem of DFT was emphasized by Kohn et al.,5that proposed an ap-proach in which traditional DFT methods are modified by treating long-range interactions separately in terms of the susceptibility. In the limit of large distances, they get the usual −C6R−6 form for the dipole dispersion attraction be-tween pairs of atoms.

In an earlier work6 we have proposed a DF for the asymptotic dispersion energy by replacing the electric dipole susceptibility model based on the uniform electron gas7–9by one that satisfies a sum rule and fitting exact dipole dynamic polarizability for the hydrogen atom. Calculated C6 coeffi-cients for several dimers involving alkali, alkaline-earth, and noble gas atoms showed an unbelievably mean absolute de-viation of only 2% from results of highly accurate calcula-tions. The current paper extends the approach for all multi-pole dispersion interactions. In addition, we propound a simple vdW DF for the whole range of intermolecular sepa-rations.

When the charge distributions of the interacting atoms do not overlap appreciably, the second-order dispersion energy for two atoms A and B in their ground state can be expanded in terms of a series of inverse powers of the inter-nuclear separation R共Refs.10and11兲

E共2兲= −

m=3

C2mAB

R2m, 共1兲

where the multipole dispersion coefficients are given by12 共we use atomic units throughout兲

C2mAB=

l=1 m−2 共2m − 2兲! 2␲共2l兲 ! 共2m − 2l − 2兲!

0 ⬁ d␻ ␣l A共i ␻兲␣m−l−1 B 共i ␻兲 共2兲 with ␣l

A/B共i兲 being the dynamic 2l-pole electric polariz-ability of atom A or B at the imaginary frequency i␻.

Here we generalize for all dynamic multipole polariz-ability the local approximation8

l A共i ␻兲 =

VA d3rAl A共i,n兲, 共3兲

where␹lA共i, n兲 is the dynamic electric 2l-pole susceptibility at angle-averaged density n共rA兲, and rA is the distance from the nucleus of atom A. The integration is over the atom.

The dynamic multipole polarizabilities, in the limit of infinite frequency, must satisfy13

l A共i

兲 →l具rA2l−2

␻2 . 共4兲

The brackets represent the average over the ground-state atomic wave function. A simple input susceptibility for Eq.

共3兲 that satisfies this constraint is the Padé approximation

l A共i,n兲 =l A共0,n兲 1 +

l A共0,n兲 lrA 2l−2 n共rA

␻2 . 共5兲

Substituting Eqs. 共3兲and共5兲 in Eq.共2兲we obtain after inte-gration over frequencies

C2mAB关n兴 =

l=1 m−2 共2m − 2兲! 4共2l兲 ! 共2m − 2l − 2兲! ⫻

VA

VB d3rAd3rB cl,m−l−1 AB 关n兴, 共6兲 with a兲Electronic mail: [email protected].

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cABp,q关n兴 =p A共0,n兲q B共0,n兲

p A共0,n兲 prA 2p−2 n共rA兲 +

q B共0,n兲 qrB 2q−2 n共rB兲 . 共7兲

Thus, the DF关Eq.共6兲兴 yields any C2mABdispersion coeffi-cients provide that the static electric 2l-pole susceptibility

l A共0,n

A兲 is known. Inspired in our earlier work

6 we write ␹l A共0,n A兲 = ␣l A共0兲

rA 2l−2

fA S共n兲n共r Ancutoff A + n共r A

␯l

VA d3rA

rA 2l−2

fA S共n兲n共r AncutoffA + n共rA

␯l

, 共8兲 where ␣l A共0兲 is the static 2l

-pole polarizability for atom A, and fA S共n兲 = a +共1 − a兲关1 − e−␭A n共rA兲 1 + e−␭A关nH c−n共rA兲兴 共9兲

sets to a = 0.054 inside a core radius where the density is very

large; nH c

= 1.000; and ␭A=共ncusp

A − 0.682兲5/3 is a parameter characterizing the smoothness of the step function and ncuspA ⬅n共rA= 0兲 is the cusp density for atom A.

In performing DF calculations for C6 coefficients6 with

␯1= 1 we found that the results are sensible mainly to param-eter ncutoffA which plays the rule of low density cutoff instead of one criterion used by Rapcewicz–Aschroft,7 Andersson

et al.8 and Dobson–Dinte.9 The simple choice of ncutoffA as being the density at “polarizability radius”14–16

3␣1A共0兲 gave very good results over all dimers. Here, we keep ncutoffA ⬅n共rA=

3

␣1

A共0兲兲 for all multipole susceptibilities and we set

␯2= 0.850, ␯3= 0.827, ␯4= 0.833, ␯5= 0.870, and ␯6= 1.000 such that Eq. 共6兲 fitting the exact C2mⱕ16 dispersion coeffi-cients for hydrogen dimer.17 Finally, we get a DF for all dispersion coefficients from a parameterization based only on the exact results for hydrogen dimer. We will test this DF applying it to calculation of vdW coefficients for dimers in-volving alkali, alkaline-earth, and noble gas atoms. We ex-tract the atomic charge densities from available Roothaan– Hartree–Fock wave functions18–20 and the static multipole polarizabilities from references.21–29

TablesIandIIshow that both mean absolute deviations for C8and C10coefficients between ours and highly accurate calculations17,23–25,27–29 are only 3%. Also, we calculate the second-order C12, C14, and C16 coefficients for hydrogen-alkali and hydrogen-alkali-hydrogen-alkali dimers and, similarly, the results 共Table III兲 are very close to those currently considered as

reference values,17,29 with mean absolute deviations of 4%, 5% and 6%, respectively.

Our accurate DF 关Eqs. 共6兲–共9兲兴 can be useful of two ways:共i兲 It can substitute the semiempirical fits of dispersion coefficients present in the dispersion corrected DFT approach30–42 and, more important, 共ii兲 it can be used to mapping the nonlocal part of the correlation energy43–47by

TABLE I. C8and C10dispersion coefficients共in atomic units兲 calculated in

this work and from accurate many-body calculations.共Refs.17,23–25, and

27–29兲, X共n兲=X⫻10n.

Atom pairs C8 Ref. C10 Ref.

H–H 124.4 124.4 3285.7 3285.8 –Li 3150 3280 217418 223017 –Na 3887 4059 2.87共5兲 2916 –K 8073 7970 7.54共5兲 7.344共5兲 –Rb 10031 9540 9.90共5兲 9.301共5兲 –Cs 14499 1.57共6兲 Li–Li 8.14共4兲 8.34共4兲 7.16共6兲 7.35共6兲 –Na 9.52共4兲 9.88共4兲 8.84共6兲 9.16共6兲 –K 1.93共5兲 1.95共5兲 2.08共7兲 2.10共7兲 –Rb 2.35共5兲 2.34共5兲 2.64共7兲 2.61共7兲 –Cs 3.36共5兲 3.21共5兲 4.03共7兲 3.84共7兲 Na–Na 1.10共5兲 1.16共5兲 1.08共7兲 1.13共7兲 –K 2.17共5兲 2.24共5兲 2.48共7兲 2.53共7兲 –Rb 2.63共5兲 2.66共5兲 3.13共7兲 3.13共7兲 –Cs 3.72共5兲 3.62共5兲 4.72共7兲 4.55共7兲 K–K 4.15共5兲 4.20共5兲 5.37共7兲 5.37共7兲 –Rb 4.95共5兲 4.93共5兲 6.68共7兲 6.60共7兲 –Cs 6.86共5兲 6.62共5兲 9.86共7兲 9.40共7兲 Rb–Rb 5.87共5兲 5.77共5兲 8.26共7兲 7.96共7兲 –Cs 8.06共5兲 7.69共5兲 12.1共7兲 11.3共7兲 Cs–Cs 10.9共5兲 10.2共5兲 17.6共7兲 15.9共7兲 Be–Be 1.04共4兲 1.022共4兲 5.23共5兲 5.165共5兲 –Mg 2.06共4兲 2.082共4兲 1.22共6兲 1.232共6兲 –Ca 5.20共4兲 5.007共4兲 3.83共6兲 3.713共6兲 –Sr 7.03共4兲 6.645共4兲 5.62共6兲 5.354共6兲 Mg–Mg 3.99共4兲 4.164共4兲 2.73共6兲 2.817共6兲 –Ca 9.83共4兲 9.807共4兲 8.12共6兲 8.088共6兲 –Sr 1.31共5兲 1.294共5兲 1.17共7兲 1.149共7兲 Ca–Ca 2.32共5兲 2.260共5兲 2.28共7兲 2.200共7兲 –Sr 3.05共5兲 2.956共5兲 3.22共7兲 3.068共7兲 Sr–Sr 4.00共6兲 3.854共6兲 4.50共7兲 4.250共7兲

TABLE II. C8and C10dispersion coefficients共in atomic units兲 calculated in

this work and from accurate many-body calculations.共Refs.17,23–25, and

27–29兲, X共n兲=X⫻10n.

Atom pairs C8 Ref. C10 Ref.

He–He 14.47 14.11 189.7 183.6 –Ne 36.82 36.18 557.2 545.1 –Ar 168.8 167.5 3797 3701 –Kr 274.7 280.0 7349 7257 –Xe 508.8 525.0 16823 16674 Ne–Ne 90.98 90.34 1556 1536 –Ar 392.8 390.1 9529 9335 –Kr 624.3 638.1 17772 17658 –Xe 1126 1162 39138 38978 Ar–Ar 1642 1623 50096 49063 –Kr 2570 2617 88334 88260 –Xe 4540 4669 183535 184250 Kr–Kr 3985 4187 151869 155450 –Xe 6957 7389 306308 316030 Xe–Xe 11928 12807 594677 619840

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Ec nl关n兴 = −

⍀A

⍀B d3rAd3rB

m=3D2m共rAB兲 ⫻

l=1 m−2 共2m − 2兲! 共2l兲 ! 共2m − 2l − 2兲! cl,m−l−1AB 关n兴 rAB 2m

, 共10兲

where rAB=兩rA− rB兩 and ⍀A/B is the atomic basin48,49 of the atom A/B.

If we set D2m共r兲=1, this long-range functional is just an

ad hoc generalization of the dipole-dipole dispersion

interac-tion DF, derived first by Rapcewicz–Aschroft,7 for all 共second-order兲 multipole dispersion interactions. The need for damping functions,50,51 D2m共r兲, arises from the fact that the expansion 关Eq. 共1兲兴 becomes physically unrealistic at small interatomic distances where charge overlap effects are relevant. Using the triplet H2 as reference system, Douketis

et al.52 propose for these damping functions the expression

D2m共r兲 =

1 − exp

2.1r 2m − 0.109 r2

2m

2m . 共11兲

Recent studies41,53,54suggest truncating the multipole

expan-sion in m = 5, the dipole-octopole, and

quadrupole-quadrupole interactions.

The great appeal of the functional关Eq.共10兲兴 is that 共i兲 it reproduces the first-principles dipole-dipole dispersion DF 共Refs.6–9兲; 共ii兲 it recovers the standard multipole expansion

关Eq. 共1兲兴, with damping correction, in the asymptotic limit

rAB⬇R ; and 共iii兲 it allows to calculate all second-order mul-tipole dispersion coefficients for atom-atom interaction with a very good accuracy.

Recently Becke and Johnson55–57 showed how to use Hirshfeld partition to get atomic polarizability to be used for dispersion calculations, these and other studies49,58–61 sug-gest that the extension of Eq.共10兲for vdW interactions be-tween molecules is straightforward if we generalize the Hir-shfeld scheme for all multipole polarizabilities. Moreover, Kong et al.62have shown that a postself-consistent-field ap-proach for vdW interactions constitutes a good approxima-tion. This finding greatly simplifies the implementation of the functional.

In summary, we have presented a DF approach to obtain all high-order multipole dispersion coefficients for two atoms separated by a large distance. From the encouraging results obtained for the dispersion coefficients, we proposed a DF for the long-range part of the correlation energy that can be extended for interactions between molecules.

The author is very grateful to Marilia Junqueira Caldas for helpful discussions. This work was supported by the Bra-zilian agencies CNPq, INEO/INCT-MCT, and FAPESP.

1P. Hohenberg and W. Kohn,Phys. Rev. 136, B864共1964兲. 2W. Kohn and L. J. Sham,Phys. Rev. 140, A1133共1965兲.

3J. P. Perdew, A. Ruzsinszky, J. Tao, V. N. Staroverov, G. E. Scuseria, and

G. I. Csonka,J. Chem. Phys. 123, 062201共2005兲.

4S. Kristyán and P. Pulay,Chem. Phys. Lett. 229, 175共1994兲.

5W. Kohn, Y. Meir, and D. E. Makarov,Phys. Rev. Lett. 80, 4153共1998兲. 6N. A. Lima and M. J. Caldas,Phys. Rev. B 72, 033109共R兲 共2005兲. 7K. Rapcewicz and N. W. Ashcroft,Phys. Rev. B 44, 4032共1991兲. 8Y. Andersson, D. C. Langreth, and B. I. Lundqvist,Phys. Rev. Lett. 76,

102共1996兲.

9J. F. Dobson and B. P. Dinte,Phys. Rev. Lett. 76, 1780共1996兲. 10A. Dalgarno and W. D. Davison,Adv. At. Mol. Phys. 2, 1共1966兲. 11A. Dalgarno,Adv. Chem. Phys. 12, 143共1967兲.

12S. H. Patil and K. T. Tang,J. Chem. Phys. 106, 2298共1997兲. 13D. Rosenthal, R. P. McEachran, and M. Cohen,Proc. R. Soc. London,

Ser. A 337, 365共1974兲.

14L. Pauling, General Chemistry共W. H. Freeman and Company, San

Fran-cisco, 1970兲, p. 395.

15J. K. Nagle,J. Am. Chem. Soc. 112, 4741共1990兲. 16R. K. Nesbet,Phys. Rev. A 56, 2778共1997兲.

17J. Mitroy and M. W. J. Bromley,Phys. Rev. A 71, 032709共2005兲. 18A. D. McLean and R. S. MacLean,At. Data Nucl. Data Tables 26, 197

共1981兲.

19C. F. Bunge, J. A. Barrientos, A. V. Bunge, and J. A. Cogordan,Phys.

Rev. A 46, 3691共1992兲.

20C. F. Bunge, J. A. Barrientos, and A. V. Bunge,At. Data Nucl. Data

Tables 53, 113共1993兲.

21F. N. Yousif, V. K. Tondon, and G. C. Shukla,Phys. Rev. A 17, 1269

共1978兲.

22A. Kumar and W. J. Meath,Can. J. Chem. 63, 1616共1985兲. 23A. J. Thakkar,J. Chem. Phys. 75, 4496共1981兲.

24A. J. Thakkar, H. Hettema, and P. E. S. Wormer,J. Chem. Phys.97, 3252

TABLE III. Second-order C12, C14, and C16 dispersion coefficients 共in

atomic units兲 calculated in this work and from accurate calculations. 共Refs.

17and29兲, X共n兲=X⫻10n.

Atom pairs C12 Ref. C14 Ref.

H–H 1.215共5兲 1.215共5兲 6.061共6兲 6.061共6兲 –Li 2.10共7兲 2.66共9兲 –Na 2.96共7兲 4.10共9兲 –K 9.92共7兲 1.73共10兲 –Rb 1.45共8兲 2.55共10兲 Li–Li 8.78共8兲 9.015共8兲 1.42共11兲 1.455共11兲 –Na 1.13共9兲 1.92共11兲 –K 3.09共9兲 6.05共11兲 –Rb 4.08共9兲 8.30共11兲 Na–Na 1.45共9兲 1.500共9兲 2.56共11兲 2.602共11兲 –K 3.82共9兲 7.73共11兲 –Rb 5.01共9兲 1.05共12兲 K–K 9.27共9兲 9.102共9兲 2.09共12兲 2.000共12兲 –Rb 1.19共10兲 2.76共12兲 Rb–Rb 1.52共10兲 1.426共10兲 3.64共12兲 3.314共12兲

Atom pairs C16 Ref.

H–H 3.926共8兲 3.938共8兲 –Li 4.10共11兲 –Na 7.36共11兲 –K 3.90共12兲 –Rb 5.97共12兲 Li–Li 2.92共13兲 2.997共13兲 –Na 4.14共13兲 –K 1.51共14兲 –Rb 2.14共14兲 Na–Na 5.75共13兲 5.736共13兲 –K 1.99共14兲 –Rb 2.80共14兲 K–K 5.96共14兲 5.544共14兲 –Rb 8.10共14兲 Rb–Rb 10.9共14兲 9.656共14兲

(5)

共1992兲.

25Z. C. Yan, J. F. Babb, A. Dalgarno, and G. W. F. Drake,Phys. Rev. A54,

2824共1996兲.

26A. Derevianko, W. R. Johnson, M. S. Safronova, and J. F. Babb,Phys.

Rev. Lett. 82, 3589共1999兲.

27S. G. Porsev and A. Derevianko,J. Chem. Phys. 119, 844共2003兲. 28J. Mitroy and M. W. J. Bromley,Phys. Rev. A 68, 052714共2003兲. 29J. Mitroy and M. W. J. Bromley,Phys. Rev. A 71, 042701共2005兲. 30M. Elstner and P. Hobza,J. Chem. Phys. 114, 5149共2001兲.

31X. Wu, M. C. Vargas, S. Nayak, V. Lotrich, and G. Scoles,J. Chem. Phys.

115, 8748共2001兲.

32Q. Wu and W. Yang,J. Chem. Phys. 116, 515共2002兲.

33M. Hasegawa and K. Nishidate,Phys. Rev. B 70, 205431共2004兲. 34S. Grimme,J. Comput. Chem. 25, 1463共2004兲.

35S. Grimme, J. Antony, T. Schwabe, and C. Mück-Lichtenfeld,Org.

Bio-mol. Chem. 5, 741共2007兲.

36L. Zhechkov, T. Heine, S. Patchkovskii, G. Seifert, and H. A. Duarte,J.

Chem. Theory Comput. 1, 841共2005兲.

37M. A. Neumann and M.-A. Perrin,J. Phys. Chem. B109, 15531共2005兲. 38F. Ortmann, F. Bechstedt, and W. G. Schmidt,Phys. Rev. B73, 205101

共2006兲.

39F. Ortmann, W. G. Schmidt, and F. Bechstedt, Phys. Rev. Lett. 95,

186101共2005兲.

40J. F. Dobson, J. Wang, B. P. Dinte, K. McLennan, and H. M. Le,Int. J.

Quantum Chem. 101, 579共2005兲.

41A. Ruzsinszky, J. P. Perdew, and G. I. Csonka,J. Phys. Chem. A 109,

11015共2005兲.

42J.-M. Ducéré and L. Cavallo,J. Phys. Chem. B 111, 13124共2007兲. 43M. Dion, H. Rydberg, E. Schröder, D. C. Langreth, and B. I. Lundqvist,

Phys. Rev. Lett. 92, 246401共2004兲.

44D. C. Langreth, M. Dion, H. Rydberg, E. Schroder, P. Hyldgaard, and B.

I. Lundqvist,Int. J. Quantum Chem. 101, 599共2005兲.

45T. Thonhauser, V. R. Cooper, S. Li, A. Puzder, P. Hyldgaard, and D. C.

Langreth,Phys. Rev. B 76, 125112共2007兲.

46D. C. Langreth, B. I. Lundqvist, S. D. Chakarova-Käck, V. R. Cooper, M.

Dion, P. Hyldgaard, A. Kelkkanen, J. Kleis, L. Kong, S. Li, P. G. Moses, E. Murray, A. Puzder, H. Rydberg, E. Schröder, and T. Thornhauser,J. Phys.: Condens. Matter 21, 084203共2009兲.

47J. F. Dobson and J. Wang,Phys. Rev. Lett. 82, 2123共1999兲.

48R. F. W. Bader, W. H. Henneker, and P. E. Cade,J. Chem. Phys.46, 3341

共1967兲.

49F. L. Hirshfeld,Theor. Chim. Acta 44, 129共1977兲.

50T. Sato, T. Tsuneda, and K. Hirao,J. Chem. Phys. 123, 104307共2005兲. 51M. Rapacioli, F. Spiegelman, D. Talbi, T. Mineva, A. Goursot, T. Heine,

and G. Seifert,J. Chem. Phys. 130, 244304共2009兲.

52C. Douketis, G. Scoles, S. Marchetti, M. Zen, and A. J. Thakkar, J.

Chem. Phys. 76, 3057共1982兲.

53A. Olasz, K. Vanommeslaeghe, A. Krishtal, T. Veszprémi, C. Van

Alse-noy, and P. Geerlings,J. Chem. Phys. 127, 224105共2007兲.

54F. O. Kannemann and A. D. Becke,J. Chem. Theory Comput. 5, 719

共2009兲.

55A. D. Becke and E. R. Johnson,J. Chem. Phys. 124, 014104共2006兲. 56E. R. Johnson and A. D. Becke,J. Chem. Phys. 124, 174104共2006兲. 57A. D. Becke and E. R. Johnson,J. Chem. Phys. 123, 154101共2005兲. 58A. Krishtal, P. Senet, M. Yang, and C. Van Alsenoy,J. Chem. Phys. 125,

034312共2006兲.

59A. Krishtal, K. Vanommeslaeghe, A. Olasz, T. Veszprémi, C. Van

Alse-noy, and P. Geerlings,J. Chem. Phys. 130, 174101共2009兲.

60F. De Proft, C. Van Alsenoy, A. Peeters, W. Langenaeker, and P.

Geer-lings,J. Comput. Chem. 23, 1198共2002兲.

61F. De Proft, R. Vivas-Reyes, A. Peeters, C. Van Alsenoy, and P.

Geer-lings,J. Comput. Chem. 24, 463共2003兲.

62J. Kong, Z. Gan, E. Proynov, M. Freindorf, and T. R. Furlani,Phys. Rev.

A 79, 042510共2009兲.

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A análise documental foi desenvolvida em três dos quatro estudos realizados: DOCÊNCIA EM SAÚDE: PROPOSTAS, CONCEPÇÕES E PRÁTICAS DE FORMAÇÃO/DESENVOLVIMENTO,

Por sua vez, o quinino e a cafeína, alcaloides com grande atividade fisiológica, são utilizados na produção e preparação de vários géneros alimentícios, como as bebidas