2
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Why the total energy calculated with GGA and metaGGA=SCAN are so different? My INNCAR file is

 **PREC = Accurate
 ISTART=0                       
 ICHARG=2                       
 ENCUT=520                     
 NELM=40                      
 ISMEAR=0
 SIGMA=0.05                     
Dynamic:
 ISIF=3                         
 IBRION=2                       
 ISYM = 2
 NSW=200                        
 EDIFF = 0.00001
 EDIFFG = -0.01                  
Mix:
 LMAXMIX=4
 METAGGA=SCAN
 ALGO = ALL
 LASPH = .TRUE.
#ADDGRID = .TRUE.
 LDIAG =.FALSE.
#LUSE_VDW = .TRUE.
#BPARAM = 15.7
Paralellisation:
 NCORE = 4
Output:
 LCHARG=.FALSE.                 
 LWAVE=.FALSE.***                  
 
The output for Si
In GGA
FREE ENERGIE OF THE ION-ELECTRON SYSTEM (eV)
  ---------------------------------------------------
  free  energy   TOTEN  =       -10.84990789 eV


In metaGGA=scan
FREE ENERGIE OF THE ION-ELECTRON SYSTEM (eV)
  ---------------------------------------------------
  free  energy   TOTEN  =       -20.01529337 eV
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  • $\begingroup$ Have you remembered to use a SCAN pseudopotential? $\endgroup$ Aug 26, 2023 at 16:01
  • $\begingroup$ Sorry, I am not very familiar with DFT calculations, I just wanted to check the formation in two ways. I do not understand the exact meaning of your question. Does the meta GGA SCAN have different pseudo in contrast the GGA? I just chek kinetic in POTCAR. $\endgroup$
    – babak ab
    Aug 26, 2023 at 18:21
  • 2
    $\begingroup$ Yes, you should always try to use a pseudopotential with the sam XC functional (or similar), otherwise your core and Valence electrons are being modelled with different physics. The actual Kohn-Sham energy value in a pseudopotential calculation doesn't mean anything, because there's an arbitrary energy shift. Energy differences are the physically meaningful quantities. $\endgroup$ Aug 27, 2023 at 21:12

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