[QE-users] QHA Error: from find_min_mur_pol : error # 1 minimum not found

[Sitangshu Bhattacharya]

Dear all,

I am trying to do a QHA analyses of a material with symmorphic group D_3h
with space group P63/mmc. A BZ sampling was done at unshifted 12x12x1 with
q-point sampling as 10x10x1.
I have choosen three geometries (two about the central relaxed one) and
obtained the minimum energy configuration:

# Vol.        E_calc        E_fit       E_diff    Pressure      Enthalpy
# a.u.^3        Ry           Ry            Ry        GPa           Ry
##########################################################################
 3810.76     -26.83684     -26.83684     0.00000       0.05      -26.82358
 3835.17     -26.83688     -26.83688    -0.00000       0.00      -26.83667
 3859.69     -26.83684     -26.83684    -0.00000      -0.05      -26.84946

The dynamical matrices were calculated and all the phonon dispersion, free
energy, etc. were done at all geometries. I found that the results upto
this stage are quite convincing.

However during the end, when the anharmonic computation (mur_lc_t) started,
I got this horrible error:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Error in routine find_min_mur_pol (1):
     minimum not found
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

     stopping ...

I used temperature variation from 0K to 1000K with difference of 3K. and
the geometries are seperated by 0.01 angstrom about the central one.
I was using QE-6.1 version. I am not getting any clue wher I am wrong.. Any
suggestion will be greatly appreciated!
Excuse me for writng in the QE forum. I saw that the QHA forum has become
obsolate....



Regards,
**********************************************
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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