Symmetry breaking in ZORA-NMR calculations


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Dear NWChem friends

I calculated NMR in [PtCl4]2- by ZORA in NWChem6.3. [PtCl4]2- has D4h symmetry. The calculated isotropic shielding constants of Cl atoms are 1159.6608, 1175.3171, 1162.2551, and 1148.9335 ppm. These are significantly different to each other, that is, symmetry breaking occurs. I want to know why it happens.
In addition, isotropic shielding constant of Pt is -1140.1492 ppm.

Best regards,

Input file is as follows
ECHO
START
TITLE "[PtCl4]-2"
CHARGE -2
BASIS SPHERICAL
 Pt library sarc-zora
Cl library 6-31G*
END
memory 500 mb
DFT
 XC pbe0
direct
ITERATIONS 150
END
RELATIVISTIC
 ZORA
CLIGHT 137.0359895
END
COSMO
dielec 78.4
rsolv 0.5
ificos 1
lineq 0
do_gasphase false
END
PROPERTY
 MULLIKEN
DIPOLE
SHIELDING
END
GEOMETRY
symmetry D4h
Pt 0.0000 0.0000 0.0000
Cl 2.3040 0.0000 0.0000
END
TASK DFT energy
TASK DFT property