The CCCA module calculates the total energy using the correlation consistent Composite Approach (ccCA). At present the ccCA module is designed for the study of main group species only.
(E_{ccCA} = \Delta E_{MP2/CBS} ; ; + \Delta E_{CC} + \Delta E_{CV} + \Delta E_{SR} + \Delta E_{ZPE})
where EMP2/CBS is the complete basis set extrapolation of MP2 energies with the aug-cc-pVnZ (n=T,D,Q) series of basis sets, (\Delta E_{CC}) is the correlation correction,
(\Delta E_{CC} = E_{CCSD(T)/cc-pVTZ} ; ; ; - E_{MP2/cc-pVTZ})
(\Delta E_{CV}) is the core-valence correction,
(\Delta E_{CV} = E_{MP2(FC1)/aug-cc-pCVTZ} ; ; ; ; ; - E_{MP2/aug-cc-pVTZ})
(\Delta E_{SR}) is the scalar-relativistic correction,
(\Delta E_{SR} = E_{MP2/cc-pVTZ-DK} ; ; ; - E_{MP2/cc-pVTZ})
and (\Delta E_{ZPE}) is the zero-point energy correction or thermal correction. Geometry optimization and subsequent frequency analysis are performed with B3LYP/cc-pVTZ.
Suggested reference: N.J. DeYonker, B. R. Wilson, A.W. Pierpont, T.R. Cundari, A.K. Wilson, Mol. Phys. 107, 1107 (2009). Earlier variants for ccCA algorithms can also be found in: N. J. DeYonker, T. R. Cundari, A. K. Wilson, J. Chem. Phys. 124, 114104 (2006).
The ccCA module can be used to calculate the total single point energy for a fixed geometry and the zero-point energy correction is not available in this calculation. Alternatively the geometry optimization by B3LYP/cc-pVTZ is performed before the single point energy evaluation. For open shell molecules, the number of unpaired electrons must be given explicitly.
CCCA
[(ENERGY||OPTIMIZE) default ENERGY]
[(DFT||DIRECT) default DFT]
[(MP2||MBPT2) default MP2]
[(RHF||ROHF||UHF) default RHF]
[(CCSD(T)||TCE) default CCSD(T)]
[NOPEN <integer number of unpaired electrons default 0 >]
[(THERM||NOTHERM) default THERM]
[(PRINT||NOPRINT) default NOPRINT]
[BASIS <basis name for orbital projection guess>]
[MOVEC <file name for orbital projection guess>]
END
One example of input file for single point energy evaluation is given here:
start h2o_ccca
title "H2O, ccCA test"
geometry units au
H 0.0000000000 1.4140780900 -1.1031626600
H 0.0000000000 -1.4140780900 -1.1031626600
O 0.0000000000 0.0000000000 -0.0080100000
end
task ccca
An input file for the ground state of O2 with geometry optimization is given below:
start o2_ccca
title "O2, ccCA test"
geometry units au
O 0.0000000000 0.0000000000 -2.0000
O 0.0000000000 0.0000000000 0.0000
end
ccca
optimize
dft
nopen 2
end
task ccca