MOLPRO

46 BASIS SET EXTRAPOLATION 344
extrapolate,basis=avtz:avqz:av5z,method r=ex1,npc=2
method r determines the method for extrapolating the reference energy (in this case a single
exponential); npc=2 means that only the last two energies should be used to extrapolate the
correlation energy (by default, a least square fit to all given energies is used). This yields
BASIS EREF ECORR ETOT
AVTZ -76.06061330 -0.28167606 -76.34228936
AVQZ -76.06600082 -0.29758099 -76.36358180
AV5Z -76.06732050 -0.30297495 -76.37029545
CBS -76.06774863 -0.30863419 -76.37638283
Rather than using the default procedure as above, one can also specify a procedure used to carry
out the energy calculation, e.g.
extrapolate,basis=avtz:avqz:av5z,proc=runccsd, method_r=ex1,npc=2}
procedure runccsd
hf
ccsd(t)
endproc
Alternatively, the energies can be provided via variables EREF, ECORR, ETOT etc. These must
be vectors, holding as many values as basis sets are given.
46.1 Options
The possible options and extrapolation methods are:
BASIS=basissets
PROC=procname
STARTCMD=command
METHOD=key
METHOD C=key
METHOD R=key
VARIABLE=name
ETOT=variable
EREF=variable
Specify as set of correlation consistent basis sets, separated by colons.
Specify a procedure to run the energy calculations
Start command for the energy calculations: the sequence of commands
from STARTCMD and the current EXTRAPOLATE is run. STARTCMD
must come before the extrapolate command in the input.
Specifies a keyword to define the extrapolation function, see section
46.2.
Specifies a keyword to define the extrapolation function for the correlation
energy, see section 46.2.
Specifies a keyword to define the extrapolation function for the reference
energy, see section 46.2.
Specifies a variable name; this variable should contain the energies to
be extrapolated.
Provide the total energies in variable (a vector with the same number
of energies as basis sets are given) If only ETOT but not EREF is
given, the total energy is extrapolated.
Provide the reference energies to be extrapolated in variable (a vector
with the same number of energies as basis sets are given)