[Pw_forum] rVV10 calculations in espresso 5.1

[Paolo Giannozzi]

The correct DFT label for rVV10 is "rVV10", not "vv10". By 
setting "vv10", all you get is the nonlocal part, with no
other XC contributions. The output is misleading:
     Exchange-correlation      = VV10 ( 0  0  0  0 3)
but the four 0's mean respectively "no exchange", "no correlation", 
"no gradient correction to exchange", "no grad. corr. to correlation".
In the svn version there is a further check to prevent this kind of 
misunderstanding, but it was added only recently.

Paolo

On Thu, 2014-10-16 at 12:03 +0100, Andrea Floris wrote:
> Dear quantum-ESPRESSO users,
> 
> 
> I am running some calculations with espresso 5.1 and the van der
> Waals 
> rVV10 functional. 
> 
> 
> First, with the program: 
> 
> 
> generate_rVV10_kernel_table.x
> 
> 
> 
> 
> I generated the universal file:
> 
> 
> rVV10_kernel_table
> 
> 
> 
> 
> 
> 
> 
> Then I tried  three systems up to now,
> 
> 1. two water molecules  (insulating)
> 2. a surface with some organic molecules on top (insulating). This is
> the system I am actually interested in.
> 3. graphite, with  some smearing
> 
> 
> In the first two cases 
> the energy seems to reach convergence but then
> suddenly the scf accuracy increases , like this
> 
> 
> estimated scf accuracy    <       0.06260677 Ry
>      estimated scf accuracy    <       0.04294545 Ry
>      estimated scf accuracy    <       0.02031181 Ry
>      estimated scf accuracy    <       0.01888999 Ry
>      estimated scf accuracy    <       0.01019674 Ry
>      estimated scf accuracy    <       0.00222739 Ry
>      estimated scf accuracy    <       0.00317661 Ry
>      estimated scf accuracy    <       0.00370097 Ry
>      estimated scf accuracy    <       0.00396386 Ry
>      estimated scf accuracy    <       0.00018021 Ry
>      estimated scf accuracy    <       1.54950129 Ry
>      estimated scf accuracy    <       1.54973018 Ry
>      estimated scf accuracy    <       1.54679045 Ry
> 
> 
> 

> ...and so on and does not converge after 100 steps. I tried to reduce
> the mixing to 0.1, or even smaller, without any effect. (see
> attachments)
> 
> 
> For the more complex surface+molecules system, the behaviour is
> similar.
> 
> 
> For the graphite with some smearing, the eigenvectors of the
> Hamiltonian fail to converge in the diagonalization process. (see
> attachment)
> 
> 
> I would appreciate some help to ascertain if: 
> 
> 

> 




> 1.  I am doing something wrong somewhere? 
> 2. there is an issue in the convergence of rVV10 with insulators?
> 3. is there a (different) issue with rVV10 and smearing? 
> 
> 
> I am aware that water calculations with rVV10 have been successfully
> performed, so I would  appreciate very much your suggestions.
> 
> 
> Thanks
> 
> 
> Best,
> Andrea
> 
> 
> -- 
>  Dr Andrea Floris
>  Research Associate
>  King's College London
>  Strand, London WC2R 2LS
>  United Kingdom
>  Phone: +44 (0) 207 848 2064
>  Fax    : +44 (0) 207 848 2420
>  Location:  Strand Building, 4th floor, Room 4.02 
>  Emails: andrea.floris at kcl.ac.uk, an.floris at gmail.com
> 
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> 
> 

-- 
 Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
 Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
 Phone +39-0432-558216, fax +39-0432-558222