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Your question is very general and very difficult, so that a general answer is impossible, and a detailed answer depends strongly on your system features and on your purposes. I can therefore only suggest you that unless you are interested in very fine details a standard GGA functional should behave decently in describing H-bonds, provided that you combine the electrostatic interactions inscribed in the GGA description with one of the (semiempirical or ab initio) models that add long-range dispersion forces. HTH Giuseppe Quoting ZARA NBSH <z.nr...@gmail.com>: > Dear all > > I would like to study the interaction between two organic molecules > (contains C, H and O atoms). > It seems that hydrogen-bonding between H and O atoms of different molecules > play an important role. > > My question is that what is the best method to study this system? > Could usual DFT (GGA for example blyp PP) have a correct prediction of this > system? > > I really appreciate your help in advance. > > WBR > -NN -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et égaux en droits. Les distinctions sociales ne peuvent être fondées que sur l'utilité commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la liberté, la propriété, la sûreté et la résistance à l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <giuseppe.matti...@ism.cnr.it> http://www.ism.cnr.it/en/staff/giuseppe-mattioli/ ResearcherID: F-6308-2012 _______________________________________________ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum