The following sections give short summaries of the various coupled-cluster based methods available in Q-Chem, most of which are variants of coupled-cluster theory. The basic object-oriented tools necessary to permit the implementation of these methods in Q-Chem was accomplished by Anna Krylov and David Sherrill, working at Berkeley with Martin Head-Gordon, and then continuing independently at the University of Southern California and Georgia Tech, respectively. While at Berkeley, Krylov and Sherrill also developed the optimized orbital coupled-cluster method, with additional assistance from Ed Byrd. The extension of this code to MP3, MP4, CCSD and QCISD is the work of Steve Gwaltney at Berkeley, while the extensions to QCCD were implemented by Ed Byrd at Berkeley. The original tensor library and CC/EOM suite of methods are handled by the CCMAN module of Q-Chem. Recently, a new code (termed CCMAN2) has been developed in Krylov group by Evgeny Epifanovsky and others, and a gradual transition from CCMAN to CCMAN2 has begun. During the transition time, both codes will be available for users via the CCMAN2 keyword.
CORRELATION
CORRELATION
Specifies the correlation level of theory handled by CCMAN/CCMAN2.
TYPE:
STRING
DEFAULT:
None
No Correlation
OPTIONS:
CCMP2
Regular MP2 handled by CCMAN/CCMAN2
MP3
CCMAN and CCMAN2
MP4SDQ
CCMAN
MP4
CCMAN
CCD
CCMAN and CCMAN2
CCD(2)
CCMAN
CCSD
CCMAN and CCMAN2
CC2
CCMAN2
CCSD(T)
CCMAN and CCMAN2
CCSD(2)
CCMAN
CCSD(fT)
CCMAN and CCMAN2
CCSD(dT)
CCMAN
CCVB-SD
CCMAN2
QCISD
CCMAN and CCMAN2
QCISD(T)
CCMAN and CCMAN2
OD
CCMAN
OD(T)
CCMAN
OD(2)
CCMAN
VOD
CCMAN
VOD(2)
CCMAN
QCCD
CCMAN
QCCD(T)
CCMAN
QCCD(2)
CCMAN
VQCCD
CCMAN
VQCCD(T)
CCMAN
VQCCD(2)
CCMAN
RECOMMENDATION:
Consult the literature for guidance.