Thanks, Dear Malcioglu. I downloaded the papers you referred. In fact, i think there should be some simple ways to estimate the internal energy. But it seems to be a little difficult.
Thanks. Jiayu > > So, if we want to get the real physical free energy, we should do something > else. Dear Jiayu Dai, Recently I have attended to an inspiring talk by Michiel Sprik on how to model a correct water-TiO2 interface in select cases, which, I think, the methodology may contain more or less answers related to your question. At least it certainly contains some well made remarks on what can be calculated using DFT based methods, and how it can be related to absolute values employed in chemistry. The afterwork lead to some papers that I am now working on: Phys. Chem. Chem. Phys., 2008, 10, 5238-5249 J. Phys. Chem. C, 2008, 112 (26), pp 9872?C9879 I hope you find them useful, O. Baris Malcioglu 2010/3/26 Jiayu Dai > > > > It is *NOT* any free energy of any physical system. It can be interpreted as > the free energy of a system of electrons in the field of clamped nuclei, at > the *fictitious* temperature corresponding to the smearing you use. The > reason why this concept is useful is that the free energy is variational, > while the internal energy is not. That's why Hellman-Feynman forces are > derivatives of the free energy, but not of the internal energy. > Thanks Stefano. So, if we want to get the real physical free energy, we > should do something else. As far as i know, it is difficult to estimate the > free energy. There are several methods calculating it, one of which is from > the phonon density of states. But i did not sure this method can be used at > high temperature, because the anhormanic effect is important here. > > > > Furthermore, how to get the internal energy here? The kinetic energy is easy > to calculate, but how about the potential energy? > > You do not need any internal energy. what you may actually want to estimate > is the T->0 extrapolation of both the free and internal energies (which > coincide in the T->0 limit). I think that some estimate of this are available > in the pw output, but others may know more than me about this. > Yes, what you said is what i want. Maybe from the scf calculation, we can get > something useful, cause scf gives out more information about energies. So, > could some experts can said a little about this problem? > > Thank all. > > Jiayu > > ---------------- > ------------------------------------------- > JiayuDai > DepartmentofPhysics > NationalUniversityofDefenseTechnology, > Changsha,410073,PRChina > ----------------------------------------- > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > ---------------- ------------------------------------------- Jiayu Dai Department of Physics National University of Defense Technology, Changsha, 410073, P R China ----------------------------------------- From [email protected] Fri Mar 26 12:07:15 2010 From: [email protected] (Carlo Nervi) Date: Fri, 26 Mar 2010 12:07:15 +0100 Subject: [Pw_forum] B3LYP: two conflicting matching values Message-ID: <[email protected]> Dear PWSCF users and developers, I recently tried to use the -DEXX option compiling PWSCF (17 March 2010 version), because I'd like to test b3lyp functional. Since I did not found much b3lyp PPs, I'm trying to play a little around with ld1.x and generate them. However, if I use dft='b3lyp', the ld1.x exit with the following message: from set_dft_value : error # 1 two conflicting matching values If I choose another dft (for example hse) there is no error message. Reading the source code I understood that it could be some overlapping with the blyp functional calling the set_dft_value subroutine, but I cannot go any further in my thoughts.... Anyone could give a suggestion? Thanks, Carlo P.S.: the same happens using the atomic_doc/paw_library/input/C.in by Lorenzo Paulatto if you modift dft='PBE' into dft='b3lyp'. -- ------------------------------------------------------ Carlo Nervi carlo.nervi at unito.it Tel:+39 011 6707507/8 Fax: +39 011 6707855 - Dipartimento di Chimica IFM via P. Giuria 7, 10125 Torino, Italy http://lem.ch.unito.it/
