Hello Prem Sen et alia,
Just a tiny note: If I remember correctly, C_2 has a level crossing
(very?) close to the minimum distance. So one might need to be careful to
choose the "correct" electronic ground state; I found this:
[doi: 10.1063/1.3624383]
"A particularly challenging example of this is the dissociation of the
carbon dimer, where due to its multiple bond and significant
multireference character even at equilibrium geometries, many methods
struggle.3
So Kohn-Sham method (the usual, single-determinant variant) might not be
very accurate - it depends on which level of accuracy you need.
Good Luck, :)
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari Paavo Seitsonen / [email protected] / http://www.iki.fi/~apsi/
Ecole Normale Supérieure (ENS), Département de Chimie, Paris
Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
On Wed, 1 Feb 2017, Timrov Iurii wrote:
Dear Prem Sen,
> I was trying in different way to converge scf calculation in case of carbon dimer
without "smearing". First I converge the system using
"smearing" then again I performed the scf calculation by changing the "restart_mode" from
"from_scratch" to "restart". In this condition, the scf
calculation for carbon dimer is converging & also turbo_davidson.x is possible.
Do you think, this is a right approach ??
I am not sure, but I would probably not rely on this approach. I think that if
the system is gapped, then it should be possible to converge the
ground state calculation without any intermediate calculation with a smearing.
> Also I have observed that if I am using hybrid functional, the system is
converging normally (keeping the restart_mode = from_scratch & without
"smearing").
This seems to indicate that with a hybrid functional you open a gap, and hence
no smearing is needed in the calculation.
> Can I compute the absorption spectra for a molecule having triplet ground
state using turbo_davidson.x or turbo_lanczos.x ??
If this amounts to perform a spin-polarized calculation (and include
magnetism), then these codes cannot be used because it is not
implemented (currently only spin-unpolarized calculations can be performed with
turbo_davidson.x and turbo_lanczos.x).
Regards,
Iurii
--
Dr. Iurii Timrov
Postdoctoral Researcher
Swiss Federal Institute of Technology Lausanne (EPFL)
Laboratory of Theory and Simulation of Materials (THEOS)
CH-1015 Lausanne, Switzerland
__________________________________________________________________________________________________________________________________________________
From: [email protected] <[email protected]> on behalf of prem sen
<[email protected]>
Sent: Tuesday, January 31, 2017 7:18 PM
To: [email protected]
Subject: [Pw_forum] Re : Learning TDDFT calculation in Atomic label (CH4
molecule) using turbo_lanczos.x and turbo_davidson.x
Dear Dr. Iurii Timrov,
Thanks for the reply.
I was trying in different way to converge scf calculation in case of carbon dimer without
"smearing". First I converge the system using "smearing"
then again I performed the scf calculation by changing the "restart_mode" from
"from_scratch" to "restart". In this condition, the scf calculation
for carbon dimer is converging & also turbo_davidson.x is possible. Do you
think, this is a right approach ??
Also I have observed that if I am using hybrid functional, the system is converging
normally (keeping the restart_mode = from_scratch & without
"smearing").
Can I compute the absorption spectra for a molecule having triplet ground state
using turbo_davidson.x or turbo_lanczos.x ??
Thanks & regards,
Prem Sen
Ph.D. Student,
IIT Bombay,
Mumbai,India.
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