ORCA

Basic input file

#
# My first ORCA calculation :-)
#
! HF SVP
* xyz 0 1
C 0 0 0
O 0 0 1.13
*

There are 3 comment lines all beginning with # symbol. Next we have our routine line(s) where we have defined HF as our method and SVP as our basis set. Finally, we have our CO molecule specified in xyz coordinates.

Optimization

! RKS B3LYP/G SV(P) TightSCF Opt
* int 0 1
C 0 0 0 0.0000
0.000
0.00
O 1 0 0 1.2029
0.000
0.00
H 1 2 0 1.1075 122.016
0.00
H 1 2 3 1.1075 122.016 180.00
*

Frequency

# any Hartree-Fock or DFT model can be used here
! RKS BP TZVP RI TZV/J
# ------------------------------------------------------
# These settings are advisable in order to minimize the
# numerical noise in the frequencies. You can/should also
# use larger integration grids, i.e. Grid4 NoFinalGrid
! TightSCF
# ------------------------------------------------------
# perform a geometry optimization first
! Opt
# ------------------------------------------------------
# Run a numerical frequency calculation afterwards
! NumFreq
# ------------------------------------------------------
# details of the frequency calculation
%freq CentralDiff true
# use central-differences
# (this is the new default)
Increment
0.005 # increment in bohr for the
# differentiation (default 0.005)
end
# ------------------------------------------------------
! bohrs
* xyz 0 1
O -1.396288 -0.075107 0.052125
O 1.396289 -0.016261 -0.089970
H -1.775703 1.309756 -1.111179
H 1.775687 0.1404431.711854
*

More information

ORCA documentation and tutorials are available here.