BD Keyword
Last Update: 6/26/2001

This method keyword requests a Brueckner Doubles calculation [60-61].

T
Requests a Brueckner Doubles calculation with a triples contribution [60] added. BD-T is a synonym for BD(T).

TQ
Requests a Brueckner Doubles calculation with triples and quadruples contributions [51] added.

FC
This indicates “frozen-core,” and it implies that inner-shells are excluded from the correlation calculation. This is the default calculation mode. Full specifies the inclusion of all electrons, and RW and Window allow you to input specific information about which orbitals to retain in the post-SCF calculation (see the discussion of the MPn keywords for an example).

MaxCyc=n
Specifies the maximum number of cycles.

Analytic energies, numerical gradients, and numerical frequencies.

The BD energy appears in the output labeled E(CORR), following the final correlation iteration:

 DE(CORR)=  -.55299518D-01    E(CORR)=     -.75019628089D+02

The energy is given in Hartrees. If triples (or triples and quadruples) were requested, the energy including these corrections appears after the above:

 Brueckner Doubles with Triples and Quadruples (BD(TQ))
 ======================================================
 Saving the triples amplitudes on disk, using 192 words of disk.
    T4(aaa)=   .00000000D+00
    T4(aab)=  -.40349028D-04
    T4(abb)=  -.40349028D-04
    T4(bbb)=   .00000000D+00
 Time for triples=         .10 seconds.
 Disk space used for TT scratch files  :          512 words
 E5TTaaa =    .00000000D+00
 E5TTaab =   -.12350750D-04
 E5TTabb =   -.12350750D-04
 E5TTbbb =    .00000000D+00
 E5TT     =   -.24701500D-04
 E5TQ2    =    .68473650D-05
 EQQ2     =   -.44495423D-04
 DE5   =   -.62349557751D-04 BD(TQ)    =   -.75019771137D+02

The section gives information about the computation of the non-iterative triples and quadruples correction. The final energy appears in the last line, labeled BD(TQ).

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