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I am calculating the lattice parameter of CeO2 with VASP, but the optimized lattice parameter is wrong according to many references (Physical Review B 75, 035109 (2007); The Journal of Chemical Physics 136, 041101 (2012)). In these references the optimized lattice parameter a = 5.4~5.5, while the optimized lattice parameter of my calculation is 5.7~5.8. I did some trials (I list them below), but the results did not improve. I wonder if somebody could give me some help.

My INCAR file:

SYSTEM  = CeO2    
NPAR   = 4    
PREC   = Accurate    
ISTART = 0    
ICHARG = 2    
LWAVE  = .False.    
LCHARG = .False.    
LORBIT = 11

ENCUT  = 650    
NELM   = 60    
EDIFF  = 1E-6    
LREAL  = .FALSE.    
IBRION = 2

ISIF   = 3    
NSW    = 100    
EDIFFG = -0.01

ISMEAR = -5     
LDAU = .TRUE.     
LDAUTYPE = 2
LDAUL = 3 -1    
LDAUU = 5.5 0
LDAUJ = 0.5 0
LMAXMIX = 6 

POSCAR:

Ce4 O8
1.0    
5.467450 0.000000 0.000000    
0.000000 5.467450 0.000000    
0.000000 0.000000 5.467450    
Ce O    
4 8    
direct    
0.000000 0.000000 0.000000 Ce    
0.000000 0.500000 0.500000 Ce    
0.500000 0.000000 0.500000 Ce    
0.500000 0.500000 0.000000 Ce    
0.250000 0.250000 0.750000 O    
0.250000 0.750000 0.750000 O    
0.250000 0.750000 0.250000 O    
0.250000 0.250000 0.250000 O    
0.750000 0.250000 0.250000 O    
0.750000 0.750000 0.250000 O    
0.750000 0.750000 0.750000 O    
0.750000 0.250000 0.750000 O

KPOINTS:

mesh auto
0
G
8 8 8
0  0  0

POTCAR (I'm not sure if it's possible to paste it here)

POTCAR:    PAW_PBE Ce_3 06Sep2000
POTCAR:    PAW_PBE O_s 07Sep2000 

Note that I have tested the convergence of ENCUT and KPOINTS.

I have done following trials, but they do not work, the optimized parameters are still about 5.77 ~ 5.78

  1. Increasing ENCUT to 800 eV, KPOINTS to 12 12 12
  2. spin-polarized calculation with default magmom (it converges to a FM state, while CeO2 is paramagnetic)
  3. manually changed the scaling factor, and relaxed the structure with ISIF=2, then fit according to the equation of state to get the equilibrium lattice parameter
  4. relax the structure without +U terms
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  • $\begingroup$ Not sure since I did not run the calculation yet, I think POTCAR may be the source of error. At my knowledge, Ce_3 is for trivalent Ce. For tetravalent Ce like fluorite, Ce would give more reasonable result. $\endgroup$
    – mjhong
    Commented Dec 6, 2023 at 2:42
  • $\begingroup$ @mjhong thanks for your reply! the potential were choosen according to the VRHFIN povided in the references. I will try Ce instead of Ce_3. I will provide the result later $\endgroup$
    – FaDA
    Commented Dec 6, 2023 at 14:17

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