 ## Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly  Broken-symmetry HF and DFT.

Pavlo Solntsev
pavlo.solntsev@gmail.com

Dear FF users.

Could you share your experience with broken-symmetry calculation using HF and DFT? I have an example below. If i use DFT i have Sz=0, S^2 = 0 for broken-symmetry singlet. If i use HF i have Sz=0 S^2 = 1.8. Which is reasonable. Does it mean, mix=.t. works only for HF? I know, we can remove switch symmetry completely off (nosym=1), and in this case i got S^2 = 0.8 for DFT which is also acceptable. I confused why we can use full orbital symmetry within HF, but not for DFT.

Pavel.

\$SYSTEM MWORDS=50 \$END
\$CONTRL RUNTYP=energy dfttyp=bp86  \$END
\$CONTRL SCFTYP=UHF \$END
\$CONTRL MAXIT=100 \$END
\$CONTRL ICHARG=-2  MULT=1 \$END
\$BASIS GBASIS=n31 ngauss=6  \$END
\$BASIS ndfunc=1 \$END
\$guess mix=.t. \$end
\$DATA
[Cu2F6]^-2 BS singlet
Dnh 2

CU         29.0   1.5298305586   0.0000000000   0.0000000000
F           9.0   2.7561841734   1.3744839332   0.0000000000
O           8.0   0.0000000000   1.1934572146   0.0000000000
H           1.0   0.0000000000   2.1349088145   0.0000000000
\$end   Sat Dec 21 '13 7:42am   This message read 928 times