Hi all,
I am having problems forcing symmetry on this small transition metal cluster. It looks like NWchem is not able to recognize symmetry (c2h) even if I change the tolerances, and if I force the symmetry I obtain a geometry far away from what obtained with different codes (e.g. turbomole).
I am interested on the excited states of this dimer, therefore symmetry could be very handy, but if I try to do excitations with random phase approx on the optimized geometry I get instability problems, while activating the cis flag for the Tamm-Dancoff approx. generates negative excitations.
I do not know if I am doing something wrong in the input, and I will appreciate any suggestion.
START tio2_opt_c2hb3
GEOMETRY
symmetry group c2h
Ti -0.7073194 1.1604688 0.0000000
Ti 0.7073194 -1.1604688 0.0000000
O 0.0415349 -2.6445686 0.0000000
O 0.0000000 0.0000000 -1.2512390
O 0.0000000 0.0000000 1.2512390
O -0.0415349 2.6445686 0.0000000
END
BASIS
Ti library def2-TZVP
O library def2-TZVP
END
DFT
xc B3LYP
direct
iterations 200
END
TASK DFT optimize
Thank you in advance,
Enrico