Faculty for Chemistry and Pharmacy - Group of Prof. Zipse
 

ORCA Input Files

The following ORCA input file combines two single point calculations on the methylthiyl radical (CS symmetry) at UB3LYP/6-31G(d) level in one job:

##
# test3
# UB3LYP/G 6-31G(d) sp for CH3S radical
# geom taken from G03 opt of A' state at UB3LYP/6-31G(d)
# 6-31G(d) basis using Pople-style d-exponents
#
! UKS  B3LYP/G VeryTightSCF Grid5
%basis
 Basis=_6_31G_d
end
%output
 PrintLevel=Normal
 Print[ P_Basis       ] 2
 Print[ P_GuessOrb    ] 1
 Print[ P_MOs         ] 1
 Print[ P_Density     ] 1
 Print[ P_SpinDensity ] 1
end
* xyz 0 2
C       0.004228    1.115137    0.000000
S       0.004228   -0.697639    0.000000
H      -1.047604    1.433182    0.000000
H       0.477299    1.519107    0.899333
H       0.477299    1.519107   -0.899333
*

$new_job
##
# test3
# UB3LYP/G 6-31G(d) sp for CH3S radical
# using identical geom, now calc. A'' state energy
#
! UKS  B3LYP/G VeryTightSCF Grid5
%basis
 Basis=_6_31G_d
end
%scf
 rotate {11, 12, 90, 1, 1} end
end
%output
 PrintLevel=Normal
 Print[ P_Basis       ] 2
 Print[ P_GuessOrb    ] 1
 Print[ P_MOs         ] 1
 Print[ P_Density     ] 1
 Print[ P_SpinDensity ] 1
end
* xyz 0 2
C       0.004228    1.115137    0.000000
S       0.004228   -0.697639    0.000000
H      -1.047604    1.433182    0.000000
H       0.477299    1.519107    0.899333
H       0.477299    1.519107   -0.899333
*


In the first jobs step a UB3LYP/6-31G(d) single point calculation is done starting from the default model potential guess:


! UKS  B3LYP/G VeryTightSCF Grid5
 

The "UKS" keyword calls for an unrestricted Kohn-Sham (DFT) calculation, the particular functional used being the B3LYP functional in the version also used in the Gaussian program (B3LYP/G). The keywords "VeryTightSCF" and "Grid5" control SCF convergence and numerical integration grid density, and are chosen here in a way to give good numerical accuracy. The following block of input:

%basis
 Basis=_6_31G_d
end
 

defines the basis set to be Pople's 6-31G(d) basis. Please observe that ORCA uses 5 spherical d-type polarization functions instead of the 6 cartesian d-type polarization functions used in the original development of the 6-31G(d) basis set. The number of basis functions as well as the results obtained by running the same UB3LYP/6-31G(d) calculation with ORCA and, for example, Gaussian will therefore differ slightly. It is also important to note that the exponent used for the d-type polarization functions differs slightly depending on the actual format of the input used. The example shown in the input file, or alternatively the inclusion of the keyword "6-31G(d)" together with the other keywords, results in selection of the original exponents suggested by Pople for the 6-31G basis set. The alternative format:

%basis
 Basis=_6_31G
 Pol=_d
end
 

results in the use of the exponents optimized for the 6-311++G(d) basis set. The next block of input:

%output
 PrintLevel=Normal
 Print[ P_Basis       ] 2
 Print[ P_GuessOrb    ] 1
 Print[ P_MOs         ] 1
 Print[ P_Density     ] 1
 Print[ P_SpinDensity ] 1
end
 

defines in some detail the amount of information printed to the output file. Printing the actual basis set (P_Basis) as well as the initial guess used (P_GuessOrb) helps to follow, how the SCF calculation actually starts, while all other print options (P_MOs, P_Density, P_SpinDensity) describe the results obtained after SCF convergence. The structure of the system is defined next by cartesian coordinates taken from a UB3LYP/6-31G(d) geometry optimization of the A' state in the CS point group with Gaussian:

* xyz 0 2
C       0.004228    1.115137    0.000000
S       0.004228   -0.697639    0.000000
H      -1.047604    1.433182    0.000000
H       0.477299    1.519107    0.899333
H       0.477299    1.519107   -0.899333
*
 

A trailing empty line ends the input for the first job step and the keyword:

$new_job

instructs ORCA to read additional input for the next job step. The second part included here differs from the first only by the additional input block:

%scf
 rotate {11, 12, 90, 1, 1} end
end

This command interchanges orbitals 11 and 12 (through rotation by 90 degrees), both orbitals being of the spin down type. Remembering that ORCA counts orbitals starting from 0 and also that our system contains 13 spin up (alpha) and 12 spin down (beta) electrons, this command interchanges the highest occupied beta orbital with the lowest unoccupied beta orbital. These two orbitals have different spatial orientation and this spin flip thus interconverts the A' and the A'' state.