MOLPRO

24 THE CLOSED SHELL CCSD PROGRAM 184
24.4 Singles-doubles configuration interaction, CISD
Performs closed-shell configuration interaction, CISD. The same results as with the CI program
are obtained, but this code is somewhat faster. Normally, no further input is needed. For
specifying DIIS directives, see section 24.5
24.5 The DIIS directive
DIIS,itedis,incdis,maxdis,itydis;
This directive allows to modify the DIIS parameters for CCSD, QCISD, or BCCD calculations.
itedis:
incdis:
maxdis:
itydis:
First iteration in which DIIS extrapolation may be performed (default=2).
Increment between DIIS iterations (default=1).
Maximum number of expansion vectors to be used (default=6).
DIIS extrapolation type. itydis=1 (default): residual is minimized.
itydis=2: ∆T is minimized.
In addition, there is a threshold THRDIS which may be modified with the THRESH directive.
DIIS extrapolation is only done if the variance is smaller than THRDIS.
24.6 Examples
24.6.1 Single-reference correlation treatments for H 2 O
***,h2o test
memory,1,m
!allocate 1 MW dynamic memory
geometry={o;h1,o,r;h2,o,r,h1,theta} !Z-matrix geometry input
basis=vtz
!cc-pVTZ basis set
r=1 ang !bond length
theta=104
!bond angle
hf
!do scf calculation
text,examples for single-reference correlation treatments
ci
cepa(1)
mp2
mp3
mp4
mp4;notripl
cisd
ccsd(t)
qci(t)
bccd(t)
---
!CISD using MRCI code
!cepa-1 using MRCI code
!Second-order Moeller-Plesset
!Second and third-order MP
!Second, third, and fourth-order MP4(SDTQ)
!MP4(SDQ)
!CISD using special closed-shell code
!coupled-cluster CCSD(T)
!quadratic configuration interaction QCISD(T)
!Brueckner CCD(T) calculation
http://www.molpro.net/info/current/examples/h2o_ccsd.com