[Pw_forum] Display of forces in a pure scf run

[Stefano Baroni]

Cristian,

I may have misunderstood your question, and I confess to know very little of 
the tstress and tprnfor variables, but forces in pw.x (as well as in most other 
ab-iition codes) are calculated via the Hellmann-Feynman (HF) theorem. The HF 
theorem does not require any finite displacements to calculate forces, which 
are instead used to "move" the ions (either to optimized the geometry or to 
perform ab-initio molecular dynamics).

If the question was not as simple as the answer actually implies, others may 
want ti add a less trivial answer ...

Regards,
Stefano

On Dec 6, 2011, at 6:38 PM, Cristian Degli Esposti Boschi wrote:

> Dear developers,
> 
> I have a very basic question, that I had never realized so far and has 
> been asked by a students of mine...
> 
> If I set to .TRUE. the logical fields tstress and tprnfor in the 
> &CONTROL stanza of the pw.x input during a pure scf calculation,
> how are the forces on the ions calculated? What do the displayed
> values represent if only a scf calculation is performed and
> the ionic coordinates are not allowed to change?
> 
> Thanks for your time.
> 
> -- 
> Cristian Degli Esposti Boschi
> CNR-IMM, Sezione di Bologna,
> via Gobetti, 101, 40129, Bologna, Italia
> tel. ++39 051 6399152, fax ++39 051 6399216
> degliesposti -AT- bo.imm.cnr.it
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni 
(skype)

La morale est une logique de l'action comme la logique est une morale de la 
pens?e - Jean Piaget

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[Pw_forum] Display of forces in a pure scf run

[Cristian Degli Esposti Boschi]

Dear developers,

I have a very basic question, that I had never realized so far and has 
been asked by a students of mine...

If I set to .TRUE. the logical fields tstress and tprnfor in the 
&CONTROL stanza of the pw.x input during a pure scf calculation,
how are the forces on the ions calculated? What do the displayed
values represent if only a scf calculation is performed and
the ionic coordinates are not allowed to change?

Thanks for your time.

-- 
Cristian Degli Esposti Boschi
CNR-IMM, Sezione di Bologna,
via Gobetti, 101, 40129, Bologna, Italia
tel. ++39 051 6399152, fax ++39 051 6399216
degliesposti -AT- bo.imm.cnr.it

[Pw_forum] local DOS: how to set nrmin and nrmax

[jinxi]

Dear all:
 
I try to get local DOS using projwfc.x, but i can't understand the description 
in "INPUT_projwfc": how to set parameters irmin and irmax?
I've read the input files in example16, but i still don't know how to locate 
the local DOS by irmin and irmax. Are there general methods to calculate the 
number and position of grid points?
If there are some general references (books, articles, presentations) for the 
basic knowledge, please recommend to me.
 
Many thanks!
 
best wishes
jinxi
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[Pw_forum] study the phase transition with vc-md or vc-cp

[Lily Anh]

Hi all,

Is it possible to observe the??spontaneous?phase transitions by the vc-md 
(PW.X) or vc-cp (CP.X) simulations staring from the initial structure input? If 
possible, what should we do?

Any discussion is ?helpful?

Regards & Thank you
Lily
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[Pw_forum] Display of forces in a pure scf run

[Axel Kohlmeyer]

On Tue, Dec 6, 2011 at 12:38 PM, Cristian Degli Esposti Boschi <
degliesposti at bo.imm.cnr.it> wrote:

> Dear developers,
>
> I have a very basic question, that I had never realized so far and has
> been asked by a students of mine...
>
> If I set to .TRUE. the logical fields tstress and tprnfor in the
> &CONTROL stanza of the pw.x input during a pure scf calculation,
> how are the forces on the ions calculated? What do the displayed
> values represent if only a scf calculation is performed and
> the ionic coordinates are not allowed to change?
>

since stefano already answered the first part, here an answer
to the second part. the forces and stress reported represent
the instantaneous forces and stress of the given conformation.
no more, no less. they are uniquely defined by the atom positions
and the electronic structure method (and its parameters) and
that is it. no motion needs to be considered.

ciao,
axel.



>
> Thanks for your time.
>
> --
> Cristian Degli Esposti Boschi
> CNR-IMM, Sezione di Bologna,
> via Gobetti, 101, 40129, Bologna, Italia
> tel. ++39 051 6399152, fax ++39 051 6399216
> degliesposti -AT- bo.imm.cnr.it
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>



-- 
Dr. Axel Kohlmeyer
akohlmey at gmail.com  http://goo.gl/1wk0

College of Science and Technology
Temple University, Philadelphia PA, USA.
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[Pw_forum] Query about O.pbe-rrkjus.UPF Pseudopotential

[Paolo Giannozzi]

On Dec 6, 2011, at 10:58 , Lorenzo Paulatto wrote:

> Hint: if you open it with a tex teditor you'll find this line:
>US  Ultrasoft pseudopotential

further hint: in the pseudopotential page, there is a link to a
page describing the naming convention used for UPF files:
   http://www.quantum-espresso.org/wiki/index.php/ 
Naming_convention_for_the_pseudopotential
P.
---
Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

[Pw_forum] Query about O.pbe-rrkjus.UPF Pseudopotential

[Lorenzo Paulatto]

In data 06 December 2011 alle ore 10:55:34, Shaptrishi Sharma  
 ha scritto:
> O.pbe-rrkjus.UPFa
> norm conserving pseudopotential or ultrasoft pseudopotential ?

Dear Shaptrishi,
it is ultrasoft.

Hint: if you open it with a tex teditor you'll find this line:
   US  Ultrasoft pseudopotential

best regards


-- 
Lorenzo Paulatto IdR @ IMPMC/UPMC CNRS & Universit? Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www.impmc.upmc.fr/~paulatto/
mail:  23-24/4?14 Bo?te courrier 115, 4 place Jussieu 75252 Paris C?dex 05

[Pw_forum] Query about O.pbe-rrkjus.UPF Pseudopotential

[Shaptrishi Sharma]

Hi,

is 
O.pbe-rrkjus.UPF<http://www.quantum-espresso.org/pseudo/1.3/UPF/O.pbe-rrkjus.UPF>a
norm conserving pseudopotential or ultrasoft pseudopotential ?

Best
Shapt

IIT Mumbai
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[Pw_forum] vc-md temperature increases

[Lily Anh]

Hi Paolo,

Thanks for the reply. I added the following lines in the &ions section:

? ? ntcheck=100, ? ? ? ! ?temperature is checked every ntcheck timesteps
? ? ntimes=10 ? ? ? ? ?! ?maximum number of velocity rescaling

and the calculation crashes "? ? from ?read_namelists ?: error # ? ? ? ?88
? ? ? reading namelist ions"

How to fix this?

Lily


 From: Paolo Giannozzi 
To: Lily Anh ; PWSCF Forum  
Sent: Monday, 5 December 2011, 23:10
Subject: Re: [Pw_forum] vc-md temperature increases
 
On Mon, 2011-12-05 at 17:13 +0800, Lily Anh wrote:
> 
> I am running a 'vc-md' calculation with PW.X in QE v4.1.1. The system
> is bcc-Fe supercell of 16 atoms. The target temperature were set to
> 600 K in the input file while the temperature goes up all the way to
> more than 1000 K.

velocity rescaling is present in the variable-cell MD algorithm but 
it is not actually activated. You will need to initialize variables
"ntimes" and "ntcheck", used by subroutine "vcmove" in PW/vcsubs.f90,
to the number of thermalization steps to be performed and to the 
number of steps between thermalizations; or to use the development
version (just fixed, maybe)

P.
-- 
Paolo Giannozzi, IOM-Democritos and University of Udine, Italy
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[Pw_forum] vc-md temperature increases

[Paolo Giannozzi]

On Dec 6, 2011, at 2:49 , Lily Anh wrote:

> I added the following lines in the &ions section:
>
> ntcheck=100,   !  temperature is checked every ntcheck  
> timesteps
> ntimes=10  !  maximum number of velocity rescaling
>
> and the calculation crashes "from  read_namelists  : error  
> #88

you need to modify the code, not input data

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