[Pw_forum] dismatch of Gamma phonon frequencies from different way

[黄志硕]

Dear all,
I was calculated Gamma point phonon of layered HfS2 through single point 
calculation, the results is 
 freq (1) =0.00 [cm-1]
 freq (2) =0.00 [cm-1]
 freq (3) =0.00 [cm-1]
 freq (4) =176.91 [cm-1]
 freq (5) =176.91 [cm-1]
 freq (6) =269.40 [cm-1]
 freq (7) =269.40 [cm-1]
 freq (8) =338.76 [cm-1]
 freq (9) =340.88 [cm-1]
which is consistent with Xiaokun Gu's work which had been arranged in the paper 
of http://arxiv.org/abs/1407.3758.


But when I calculated the phonon-dispersion based on a q-mesh of 4*4*1, after 
q2r.x and matdyn.x calculation, the Gamma point phonon frequency in the 
"matdyn.modes" file differed a lot:
 freq (1) = -0.07 [cm-1]
 freq (2) =-0.06 [cm-1]
 freq (3) = -0.01 [cm-1]
 freq (4) = 176.907415 [cm-1]
 freq (5) =269.403108 [cm-1]
 freq (6) =269.403108 [cm-1]
 freq (7) = 298.948294 [cm-1]
 freq (8) =338.760427 [cm-1]
 freq (9) =340.877820 [cm-1].
The parameters in the input file are: ecutwfc = 90, ecutrho = 900, conv_thr =  
1.0d-8, mixing_beta = 0.7, etot_conv_thr and forc_conv_thr are set default, and 
the K-mesh is set 17 17 2 1 1 1. During phonon calculation, "ASR" is set 
'simple'.


Before calculation, crystal structure was fully relaxed, and the convergence of 
K-mesh and cut-off of plane wave was achieved.
I also calculated the phonon-dispersion based on q mesh 4*4*2 and 8*8*1, and 
got the same results with that of q mesh 4*4*1.


I have no idea why the phonon frequencies of Gamma point get from single-point 
calculation and phonon-dispersion calculation differ so much. I will appreciate 
it if anyone could give me some instructions.

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Re: [Pw_forum] Doubt in workfunction example for Al100

[Giovanni Cantele]

The average electrostatic potential you are calculating/plotting does show 
microscopic oscillations, revealing the atomic planes
(plot the 2d column of reference/Al100.avg.out  as a function of the 1st one).

The calculation of the work function requires a “constant” energy level to 
compare the bulk and the slab calculation. For this purpose,
you run a macroscopic average of the x-y averaged electrostatic potential. The 
window you choose for the macroscopic average
is just the distance between two consecutive atomic planes (in a.u.).
Because the input positions are in alat units, you get

(2.8284271247461898 - 2.1213203435596428) * 5.4235090117 = 3.835

In this way, microscopic oscillations with period 3.835 are averaged and a 
constant level (in the inner region of the slab) is obtained.

Concerning 17.8087, in order to get this constant value, you can choose any 
position in the inner part of the slab where the
macroscopic average does not show significant variations.

Giovanni


> On 18 Mar 2015, at 10:49, Bipul Rakshit  wrote:
> 
> In espresso, there is an example to find the workfunction of Al. In the 
> run_example, the input for the the macroscopic average is the following
> cat > Al100.avg.in  < 1
> Al100.pot
> 1.D0
> 1440
> 3
> 3.83500
> EOF
> 
> In this file the quantity "3.835" i saw in average.f90 as "awin ! the 
> size of the window for macroscopic averages"
> 
> So my doubt is how we can choose this no. Can we get the information from 
> another file prerun file, like Al100.pot, or something else.
> 
> Also in run_example there is another quantity vSlab
> 
> vSlab=`grep "17.8087" Al100.avg.out | cut -d \  -f 10`
> 
> So how the value correspond to "17.8087" is assign as vSlab?
> 
> Kindly help me in this matter.
> 
> regards
> -- 
> Dr. Bipul Rakshit
> Research Associate,
> Institute of Physics (IOP),
> Bhubaneswar- 751 005
> Orissa 
> India
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-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cant...@spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele

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Re: [Pw_forum] noncolin & projwfc.x (version 5.1.1 & 5.1.2)

[Paolo Giannozzi]

On Tue, 2015-03-17 at 23:35 +0330, Mohammad Sandoghchi wrote:

> Can anybody check whether projwfc.x  works correctly in the new
> versions of Quantum Espresso (5.1.1 & 5.1.2) when "noncolin=.true." is
> used in the input files of scf and band calculations ?

YOU check. If it doesn't work, please report

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

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[Pw_forum] Doubt in workfunction example for Al100

[Bipul Rakshit]

In espresso, there is an example to find the workfunction of Al. In the
run_example, the input for the the macroscopic average is the following
cat > Al100.avg.in <___
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[Pw_forum] projected DOS

[Uri Argaman]

Dear QE users and developers

I notice that there is no implementation for the tetrahedron method for
projected DOS. Is there any way to calculate projected DOS (calculated with
projwfc.x) to get comparable results with the total DOS (calculated with
dos.x with the tetrahedron method)?

Is it possible to extract the details of the DOS using the methods
implemented in QE like features of van Hove singularities?

In addition, is there any published works using projected DOS calculated
with QE?

Recently, new codes for DOS calculations published (optados.org). Is there
a significant difference compared with the tetrahedron method as
implemented in QE?

Thank you very much


Uri Argaman

Ben-Gurion University

Israel
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