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Energy and Gradient Calculations

Energy calculations may be carried out at different levels of theory.

use modules dscf and grad or ridft and rdgrad to obtain the energy and gradient. The energy can be calculated after a define run without any previous runs. dscf and grad need no further keywords ridft and rdgrad only need the keyword $rij. The gradient calculation however requires a converged dscf or ridft run.
Density functional theory

DFT calculations are carried out in exactly the same way as Hartree-Fock calculations except for the additional keyword $dft. For DFT calculations with the fast Coulomb approximation you have to use the modules ridft and rdgrad instead of dscf and grad. Be careful: dscf and grad ignore RI-K flags and will try to do a normal calculation, but they will not ignore RI-J flags ($rij) and stop with an error message. To obtain correct derivatives of the DFT energy expression in grad or rdgrad the program also has to consider derivatives of the quadrature weights--this option can be enabled by adding the keyword weight derivatives to the data group $dft.

For a semi-direct dscf calculation (Hartree-Fock or DFT) you first have to perform a statistics run. If you type

stati dscf
nohup dscf > dscf.stat &
the disk space requirement (MB) of your current $thime and $thize combination will be computed and written to the data group $scfintunit size=integer (see Section 15.2.5). The requirement of other combinations will be computed as well and be written to the output file dscf.stat. The size of the integral file can be set by the user to an arbitrary (but reasonable) number. The file will be written until it reaches the given size and dscf  will continue in direct mode for the remaining integrals. Note that TURBOMOLE  has no 2GB file size limit.

MP2 calculations need well converged SCF runs (the SCF run has to be done with at least the density convergence $denconv 1.d-7, and $scfconv 7 as described in Section 15). This applies to CC2 or SCS-MP2 also. For MP2 calculations in the RI approximation use the ricc2 module. The input can be prepared with the cc2 menu in define. (Alternatively, the older rimp2 module and for preparation of its input the tool Rimp2prep maybe used). The module mpgrad calculates the canonical (non-RI) MP2 energy as well as the energy gradient. If only the energy is desired use the keyword $mp2energy. For all further preparations run the tool Mp2prep.
Excited states (escf)

Single point excited state energies for CIS, TDHF, and TDDFT methods can be calculated using escf. Excited state energies, gradients, and other first order properties are provided by egrad. Both modules require well converged ground state orbitals.
Excited states (ricc2)

The module ricc2 calculates MP2 and CC2 ground state energies and CIS/CCS, CIS(D), CIS(D), ADC(2) or CC2 excitation energies using the resolution-of-the-identity (RI) approximation. Excited state gradients are available at the CCS, CIS(D), ADC(2), and CC2 levels. In addition, transition moments and first-order properties are available for some of the methods. For more details see Section 9. The input can be prepared using the cc2 menu of define.

next up previous contents index
Next: Calculation of Molecular Properties Up: A `Quick and Dirty' Previous: Single Point Calculations: Running   Contents   Index