This method keyword requests a Brueckner Doubles calculation [Dykstra77, Handy89, Kobayashi91]. BD gradients are available [Kobayashi91].
T
Requests a Brueckner Doubles calculation with a triples contribution [Handy89] added. BD-T is a synonym for BD(T).
TQ
Requests a Brueckner Doubles calculation with triples and quadruples contributions [Raghavachari90] added.
FC
All frozen core options are available with this keyword. See the discussion of the FC options for full information.
MaxCyc=n
Specifies the maximum number of cycles.
Conver=N
Sets the convergence calculations to 10-N on the energy and 10-(N-2) on the wavefunction. The default is N=4 for single points and N=6 for gradients.
SaveAmplitudes
Saves the converged amplitudes in the checkpoint file for use in a subsequent calculation (e.g., using a larger basis set). Using this option results in a very large checkpoint file, but also may significantly speed up later calculations.
ReadAmplitudes
Reads the converged amplitudes from the checkpoint file (if present). Note that the new calculation can use a different basis set, method (if applicable), etc. than the original one.
Read
Reads the initial orbitals from the checkpoint file rather than doing an HF calculation. Note that the new calculation can use a different basis set than the original one.
OldFCBD
Requests old-style frozen-core BD (the core orbitals are never changed).
NewFCBD
Requests new-style frozen-core BD, in which the core orbitals are updated to conform to the BD condition T1=0, which means the BD Fock matrix is diagonal for these orbitals. This is the default.
Analytic energies and gradients for BD, numerical gradients for BD(T), and numerical frequencies for all methods. The options FC, T and TQ are not available with analytic gradients. Unrestricted open-shell calculations are available for BD energies and gradients.
The BD energy appears in the output labeled E(CORR), following the final correlation iteration:
DE(Corr)= -0.11126579 E(CORR)= -39.034559769 Delta= 2.76D-08
The energy is given in Hartrees. If triples (or triples and quadruples) were requested, the energy including these corrections appears after the preceding:
Time for triples= 0.14 seconds. T4(BD)= -0.17652187D-02 BD(T)= -0.39037034261D+02 Triples-corrected energy.
Last update: 23 April 2013