DFT does not calculate Van Der Waals. In the case of inter layer graphite, using LDA for example, you might suggest that the weak pi bonding between the layers given by DFT approximates the inter wall interaction. Steve
Dr S Bailey L & C Branch of the IoP Treasurer Physics Department Lancaster University Lancaster, UK. LA1 4YB Tel. +44(0)1524592844 ________________________________ From: Siesta, Self-Consistent DFT LCAO program, http://www.uam.es/siesta [mailto:[EMAIL PROTECTED] On Behalf Of Zeila Zanolli Sent: 04 April 2008 14:15 To: [email protected] Subject: Re: [SIESTA-L] Posible SPAM: How to calculate the interlayer inter actions of graphite using SIESTA? Dear Hao, the (ab initio calculated) interlayer distance between graphite planes is ~ 3.34 Å, while the value of the unit cell in the direction of the stacking of the layers is twice the interlayer distance, that is ~6.67 Å. See, for instance PRB 1991 vo 43 p. 4579. All the best, Zeila On 4 Apr 2008, at 14:11, Ren Hao wrote: Dear all, I'm trying to relax the geometry structure of graphite. The intralayer structures are ok, but the best interlayer distance I got is about 7.5 angstrom, which is ~12% larger than the experimental value(6.7 Ang). PBE functional and DZP basis for carbon is used in the calculation. Is there anyone has some suggestions on the calculation of van der Walls interactions between graphite layers? I would appreciate any help and advice! -- Hao Ren --------------------------------------------------------------------------------------------- Dr. Zeila Zanolli Université Catholique de Louvain (UCL) Unité Physico-Chimie et de Physique des Matériaux (PCPM) Place Croix du Sud, 1 (Boltzmann) B-1348 Louvain-la-Neuve, Belgium Phone: +32 (0)10 47 3501 Mobile: +32 (0)487 556699 Fax: +32 (0)10 47 3452 e-mail: [EMAIL PROTECTED] web: http://www.nano2hybrids.net/ ---------------------------------------------------------------------------------------------
