Example: ZORA, X2C and RA-X2C: HgI2 = Hg + I2¶
The scalar relativistic ZORA, scalar relativistic X2C, and scalar relativistic RA-X2C are compared in this example for the bond dissociation energy of HgI2 in Hg and I2. The division between scalar and spin-orbit relativistic effects is somewhat arbitrary and depends on the method of separation. Thus the scalar relativistic results of X2C and RA-X2C will be different even in the basis set limit. However, the differences for bond energies are not so large. The results for scalar relativistic ZORA are often closer to scalar relativistic RA-X2C, than to scalar relativistic X2C.
for f in "ZORA" "X2C" "RA-X2C" do $ADFBIN/adf << eor ATOMS Hg 0 0 0 I 0 0 2.554 I 0 0 -2.554 END Basis Type ZORA/DZ Core None End numericalquality good xc gga bp86 end relativistic scalar $f end input eor rm TAPE21 logfile $ADFBIN/adf << eor ATOMS I 0 0 1.333 I 0 0 -1.333 END Basis Type ZORA/DZ Core None End numericalquality good xc gga bp86 end relativistic scalar $f end input eor rm TAPE21 logfile done