[Pw_forum] Could not find the mode symmetry after phonon frequency calculation of gamma point

[Paolo Giannozzi]

Pseudopotentials do not affect symmetry. I would try to reduce the
convergence threshold for both the scf and the phonon calculation

On Mon, Jan 8, 2018 at 5:16 AM, Sitangshu Bhattacharya <
sitangshu at iiita.ac.in> wrote:

> Dear Zhishuo,
>
> Check your scf report file. This same mode symmetry should be mentioned
> there. If it is there, replace with a proper pseudo. These things comes
> when pseudos are not well tested at the initial level.
>
> Regards,
> Sitangshu
>
> On Sun, Jan 7, 2018 at 9:59 PM, 黄志硕 <zhishuohuang at gmail.com> wrote:
>
>> Dear Quantum Espresso users,
>>
>>
>>
>> I just finished the phonon calculation at Gamma point of a material with
>> T_h symmetry. But it seems that the code could not determine the mode
>> symmetry as shown in the output file:
>>
>>
>>
>> ###############################################################
>>
>>      Mode symmetry, T_h (m-3)   point group:
>>
>>
>>
>>      freq (  1 -  3) =          9.1  [cm-1]   --> T_u             I
>>
>>      freq (  4 -  6) =         14.5  [cm-1]   --> T_u             I
>>
>>      freq (  7 -  9) =         48.9  [cm-1]   --> T_g             R
>>
>>      freq ( 10 - 12) =         81.9  [cm-1]   --> T_g             R
>>
>>      freq ( 13 - 15) =        100.1  [cm-1]   --> T_u             I
>>
>>      freq ( 16 - 16) =        254.2  [cm-1]   -->   ?
>>
>>      freq ( 17 - 17) =        254.2  [cm-1]   -->   ?
>>
>>      freq ( 18 - 20) =        265.1  [cm-1]   --> T_g             R
>>
>>      freq ( 21 - 23) =        347.7  [cm-1]   --> T_u             I
>>
>>      freq ( 24 - 26) =        349.8  [cm-1]   --> T_u             I
>>
>>      freq ( 27 - 27) =        350.5  [cm-1]   --> A_u
>>
>>      freq ( 28 - 28) =        394.8  [cm-1]   -->   ?
>>
>>      freq ( 29 - 29) =        394.8  [cm-1]   -->   ?
>>
>>      freq ( 30 - 32) =        395.2  [cm-1]   --> T_u             I
>>
>>      freq ( 33 - 35) =        396.8  [cm-1]   --> T_g             R
>>
>>      freq ( 36 - 36) =        398.8  [cm-1]   -->   ?
>>
>>      freq ( 37 - 37) =        398.8  [cm-1]   -->   ?
>>
>>      freq ( 38 - 40) =        479.4  [cm-1]   --> T_g             R
>>
>> …….
>>
>> …….
>>
>> ###############################################################
>>
>>
>>
>> As from above, the code could notice the point group is T_h. However, for
>> the two-fold modes (16 and 17, 28 and 29, 36 and 37, actually, all the
>> two-fold modes have the same problem), which seem to be E_g (or E_u) mode,
>> there is no symmetry information. In stead, there is only two “?” marks.
>>
>>
>>
>> Any hint for this problem could be very welcome.
>>
>>
>>
>> Best regards
>>
>> Zhishuo Huang
>>
>>
>>
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>>
>
>
>
> --
> **********************************************
> Sitangshu Bhattacharya (সিতাংশু ভট্টাচার্য), Ph.D
> Assistant Professor,
> Room No. 2221, CC-1,
> Nanoscale Electro-Thermal Laboratory,
> Department of Electrical and Communication Engineering,
> Indian Institute of Information Technology-Allahabad
> Uttar Pradesh 211 012
> India
> Telephone: 91-532-2922000 Extn.: 2131
> Web-page: http://profile.iiita.ac.in/sitangshu/
> Institute: http://www.iiita.ac.in/
>
>
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>



-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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