[Pw_forum] Error in routine bfgs (1): NR step-length unreasonably short

[janardhan H.L.]

Dear Respected forum members,
While relaxing the slab with 'cg' diagonalization method, I have encountered 
this error (Error in routine bfgs (1): NR step-length unreasonably short). In 
bfgs_module.f90 it says the following,
|  IF ( nr_step_length < eps16 ) & CALL errore( 'bfgs', 'NR step-length 
unreasonably short', 1 )
 |


 In the forum mail archive, this error has not been mentioned. kindly let me 
know what would be the possible reasons for this error? 
Thanks and regards
Janardhan Korea Institue of Science and Technology Seoul, S.Korea



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Re: [Pw_forum] A Cutting-edge Question !!!

[ashkan shekaari]

Dear Dr. Paulatto,
Thank you so much for your quick response. I was wondering if you could
possibly inform me which line must be modified.

On Nov 14, 2016 2:05 PM, "Lorenzo Paulatto" 
wrote:

> On Monday, November 14, 2016 1:59:12 PM CET ashkan shekaari wrote:
> > Dear Matteo,
> > Thank you so much for your explanatory response.
> >
> > The very essence of my question is as follows:
> > If I want to add a term or a constant to the Hamiltonian of a given
> system,
> > which subroutine or code (*.f90) must be modified?
>
>
> PW/src/h_psi.f90
>
> but it may be harder than you expect
>
> kind regards
>
> --
> Dr. Lorenzo Paulatto
> IdR @ IMPMC -- CNRS & Université Paris 6
> phone: +33 (0)1 44275 084 / skype: paulatz
> www:   http://www-int.impmc.upmc.fr/~paulatto/
> mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
>
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Re: [Pw_forum] A Cutting-edge Question !!!

[Lorenzo Paulatto]

On Monday, November 14, 2016 1:59:12 PM CET ashkan shekaari wrote:
> Dear Matteo,
> Thank you so much for your explanatory response.
> 
> The very essence of my question is as follows:
> If I want to add a term or a constant to the Hamiltonian of a given system,
> which subroutine or code (*.f90) must be modified?


PW/src/h_psi.f90

but it may be harder than you expect

kind regards

-- 
Dr. Lorenzo Paulatto 
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05

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Re: [Pw_forum] A Cutting-edge Question !!!

[ashkan shekaari]

Dear Matteo,
Thank you so much for your explanatory response.

The very essence of my question is as follows:
If I want to add a term or a constant to the Hamiltonian of a given system,
which subroutine or code (*.f90) must be modified?

On Nov 14, 2016 12:02 PM, "Matteo Cococcioni"  wrote:

> Dear Ashkan,
>
> I'm not sure I understand your question completely, but will attempt an
> answer.
>
> First thing to keep in mind is that QE (as any other DFT code) works with
> the Kohn-Sham single particle Hamiltonian (is that what you are looking
> for?), whose eigenstates are the ones that allow you to construct the
> ground state charge density of a system and to evaluate its total energy.
> Due to the Bloch theorem (i.e. to the translational invariance of
> crystalline solids) this Hamiltonian is block-diagonal on the k-points
> (crystal momentum of electrons). Also, QE uses an expansion of Kohn-Sham
> wavefunctions on a plane-wave basis set. So, each of these blocks of the
> Hamiltonian is npw x npw where npw is the number of plane-waves used in the
> expansion of the wavefunctions of that specific k-point. QE performs an
> iterative diagonalization of each block that is involves computing the
> action of the Hamiltonian onto the current wavefunction H |psi>. This is
> done in a routine called h_psi which is the driver to compute various parts
> of the Hamiltonian and to operate it on the wavefunction. So I guess you
> can look inside that routine in order to find what you need.
>
> Best regards,
>
> Matteo
>
> On Sun, Nov 13, 2016 at 11:24 PM, ashkan shekaari 
> wrote:
>
>> Dear experts,
>>
>> How, could one derive the Hamiltonian of a given system resulting in
>> energy eigenvalues (band structure) *through the modules or subroutines*
>> included in Q. E. integrated suite?
>>
>> Is there anyway for this end?
>>
>> For example, if I provide an input scf file, how could I figure out what
>> Hamiltonian will be used in my calculations?
>>
>> How could I make a change in the Hamiltonian of a system by manipulating
>> subroutines (not the input file)?
>>
>>
>> *--*
>> *Regards,*
>> *Ashkan Shekaari*
>> *Plasma Physics Research Center*
>> *Science and Research Branch*
>> *I A U, 14778-93855 Tehran, Iran.*
>>
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>
>
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[Pw_forum] problem with pp.x in the calculation of delta rho (plot_num=9)

[Uri Argaman]

Dear QE experts
As I already mentioned in previous messages, I notice to a problem in the
calculation of delta rho. I convinced that it is not an issue of numerical
accuracy.
When I perform a calculation of delta rho with norm-conserving
pseudopotential in NaCl I get that the sum of delta rho in the xsf file is:
202.356763363 while the sum of the absolute value is: 786.819282749. It is
not seems like a numerical noise. I also check that it is in the order of
10% from the density.
When I perform the same calculation with ultrasoft pseudopotential I get
that the sum of delta rho in the xsf file is: -4.988217364  while the sum
of the absolute value is: 102.279406346.
I also notice that the number of points in the grid is different with the
different pseudopotential even though the parameters:
 e1(1) =1.0, e1(2)=0.0, e1(3) = 0.0,
 e2(1) =0.0, e2(2)=1.0, e2(3) = 0.0,
 e3(1) =0.0, e3(2)=0.0, e3(3) = 1.0,
 nx=50, ny=50, nz=50
are the same. I try to run this code with zero density to see what is the
atomic densities but I do not succeed to understand how to this. I also
have this problem in other materials with other pseudopotential. It is
possible that some pseudopotential do not fit to the calculation of delta
rho (plot_num=9)?
The input files are (for norm converving):
pw input:
 
calculation='scf',
restart_mode='from_scratch',
pseudo_dir  = '/home/uriargaman/espresso-5.4.0/pseudo',
outdir  = '/home/uriargaman/tmp15711/',
prefix='NaCl',
tstress = .true.,
tprnfor = .true.,
/
 
ibrav =2, celldm(1) =10.7789934208, nat= 2, ntyp= 2,
ecutwfc = 80
 /
 
diagonalization='david'
conv_thr = 1.0e-8
mixing_beta = 0.7
 /
 
ion_dynamics= 'bfgs'
 /
 
cell_dynamics= 'bfgs'
 /
ATOMIC_SPECIES
 Na 22.9898  Na.blyp-sp-hgh.UPF
 Cl 35.453   Cl.blyp-hgh.UPF
ATOMIC_POSITIONS (crystal)
Na   0 0 0
Cl0.5 0.5 0.5
K_POINTS (automatic)
 32 32 32 0 0 0

pp input:
 
prefix  = 'NaCl'
outdir = '/home/uriargaman/tmp15711/'
filplot = 'delta_charge'
plot_num= 9
 /
 
nfile = 1
filepp(1) = 'delta_charge'
weight(1) = 1.0
iflag = 3
output_format = 5
fileout = 'delta_rho.xsf'
e1(1) =1.0, e1(2)=0.0, e1(3) = 0.0,
e2(1) =0.0, e2(2)=1.0, e2(3) = 0.0,
e3(1) =0.0, e3(2)=0.0, e3(3) = 1.0,
nx=50, ny=50, nz=50
 /

Uri Argaman
Ben-Gurion University
Israel
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[Pw_forum] trend in HOMO-LUMO energies

[Rajdeep Banerjee]

Dear all,
 this is a question about the reliability of the trend in
HOMO-LUMO energies produced by GGA calculation. I know the absolute
HOMO-LUMO energies produced by GGA cannot be trusted.

Let us assume a model system where I have a set of clusters of different
sizes and an adsorbate molecule. I want to compare the HOMO-LUMO energies
of the molecule and the cluster with respect to vacuum (before the
adsorbate gets attached to the cluster to get an idea of the charge
transfer beforehand.)

Now, my question is, would GGA be able to correctly produce the trend in
the relative position of the adsorbate and cluster HOMO-LUMO energies (wrt
vacuum) as we increase the cluster size?

If not, what are the possible choices to get a correct trend?


I appreciate any help in this regard. Thanks in advance.

best,
-- 
Rajdeep Banerjee
PhD student
JNCASR, Bangalore
India
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Re: [Pw_forum] A Cutting-edge Question !!!

[Matteo Cococcioni]

Dear Ashkan,

I'm not sure I understand your question completely, but will attempt an
answer.

First thing to keep in mind is that QE (as any other DFT code) works with
the Kohn-Sham single particle Hamiltonian (is that what you are looking
for?), whose eigenstates are the ones that allow you to construct the
ground state charge density of a system and to evaluate its total energy.
Due to the Bloch theorem (i.e. to the translational invariance of
crystalline solids) this Hamiltonian is block-diagonal on the k-points
(crystal momentum of electrons). Also, QE uses an expansion of Kohn-Sham
wavefunctions on a plane-wave basis set. So, each of these blocks of the
Hamiltonian is npw x npw where npw is the number of plane-waves used in the
expansion of the wavefunctions of that specific k-point. QE performs an
iterative diagonalization of each block that is involves computing the
action of the Hamiltonian onto the current wavefunction H |psi>. This is
done in a routine called h_psi which is the driver to compute various parts
of the Hamiltonian and to operate it on the wavefunction. So I guess you
can look inside that routine in order to find what you need.

Best regards,

Matteo

On Sun, Nov 13, 2016 at 11:24 PM, ashkan shekaari 
wrote:

> Dear experts,
>
> How, could one derive the Hamiltonian of a given system resulting in
> energy eigenvalues (band structure) *through the modules or subroutines*
> included in Q. E. integrated suite?
>
> Is there anyway for this end?
>
> For example, if I provide an input scf file, how could I figure out what
> Hamiltonian will be used in my calculations?
>
> How could I make a change in the Hamiltonian of a system by manipulating
> subroutines (not the input file)?
>
>
> *--*
> *Regards,*
> *Ashkan Shekaari*
> *Plasma Physics Research Center*
> *Science and Research Branch*
> *I A U, 14778-93855 Tehran, Iran.*
>
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