Dear all You can do better than the semiempirical "Grimme" correction. There is a new ab initio van der Waals correlation functional implemented in QE 4.3a. Try input_dft='vdW-DF', in the &sysytem list. By the way, what about a (semiempirical or ab initio) vdW scheme in cp.x? Is there any project going on?
Yours Giuseppe Quoting Masoud Nahali <masoudnahali at gmail.com>: > Dear Eric > > Try london="true" to get improved answer; as you should know DFT is weak > to calculate dispersion forces and by using the keyword one can include > these forces semi-empirically. I hope it helps. > > Best Wishes > > Masoud > -------------- > Masoud Nahali, Sharif University of Technology > > > Eric Wrote: > > Dear all, > > I'm trying to optimize unit cell parameter of graphite. > The problem is the c axis gets too long. > Starting from published data my initial parameters are a=4.59203 Bohr > and c=12.513 Bohr. > The final values are 4.664 and 15.829 respectively. > I need someone to explain to me what I did wrong, I've attached my input > file. > That's a basic calculation so it's very frustrating to not make it done. > I thank you in advance, > > Eric. > > -- > /Be the change you wish to see in the world > / --- Mahatma Gandhi --- > > Dr. ?ric Germaneau <mailto:germaneau at gucas.ac.cn > <http://www.democritos.it/mailman/listinfo/pw_forum>> > > College of Physical Sciences > Graduate University of Chinese Academy of Sciences > Yuquan Road 19A > Beijing 100049 > China > Giuseppe Mattioli ISM-CNR Italy
