[Pw_forum] Intermolecular energy of two fragments.
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Thu Sep 18 11:13:51 CEST 2014
Dear Valentina
I suppose you have done everything you must do to subtract the basis
set superposition error (BSSE) in Gaussian... I also suppose that you
know that Gaussian uses Hartree atomic units, while QE uses Rydberg a.u.
Moreover, you should discover a little more of your work, if you want
some meaningful help. Your procedure is sound in a
plane-wave/pseudopotential framework (no BSSE...), but are you sure
you're using the very same density functional setup in Gaussian and
QE? What about dispersion forces? Which "assume_isolated" option? The
'mt' trick usually requires a supercell quite larger than the isolated
system placed therein. You should check the convergence of your
calculations wrt to such parameter.
HTH
Giuseppe
Giuseppe Mattioli
ISM-CNR
Italy
Quoting Valentina Cantatore <valecantatore at gmail.com>:
> Good morning to everyone.
>
> I would like to calculate the interaction energy between to molecules using
> QE. What I set up was to fix the dimension of a cubic box at 20 A (I think
> it is big enough to avoid interactions between the other replicated
> molecules), calculate the energy of each of the two fragments (Ea and Eb)
> and then calculate the energy of the two fragments together (Eab). What I
> expect is that interaction energy (Ein) is given by Ein=Eab-(Ea+Eb).
>
> I also used the assume_isolated option for all calculations. I sampled only
> gamma points.
>
> The results obtained are not of the same order of magnitude of those
> obtained with a gaussian basis set on the same systems.
>
> Where am I wrong? Is it possible run this kind of calculation with Quantum
> Espresso? Thank you
>
> Valentina Cantatore
> PostDoc Researcher @ Università del Piemonte Orientale
--
********************************************************
- Article premier - Les hommes naissent et demeurent
libres et ègaux en droits. Les distinctions sociales
ne peuvent être fondèes que sur l'utilitè commune
- Article 2 - Le but de toute association politique
est la conservation des droits naturels et
imprescriptibles de l'homme. Ces droits sont la libertè,
la propriètè, la sùretè et la rèsistance 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.mattioli at ism.cnr.it>
More information about the users
mailing list