[Pw_forum] rVV10 calculations in espresso 5.1

[Andrea Floris]

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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