
001111111100// 011100001110// 011000000110// 110000000011//
110000000011// 110000000011// 110000000011// 011000000110//
011100001110// 001111111100// 000011110000// 000000000000//
000000000000// 000000000000// 000000000000// 000000000000//
000000000000// 000000000000// 000000000000// 000000000000//
000000000000// 000000000000// 000000000000// 000000000000//
000000000000// 000000000000// 000000000000// 000000000000>>
#BD.8 GAUSSIAN 90 VERSION#N
#ID.8.0 Introduction to GAUSSIAN 90 version#N
0 The GAUSSIAN 90 version of the NBO program differs from
its predecessors in that the NBO segments are included as an
organic link (Link 607) of the GAUSSIAN 90 standard route,
rather than as a ``fix'' on Link 601. Default NBO analysis
is invoked by simply including the ``ExtraLinks=L607''
option on the main route card (or by adding Link 607 to any
nonstandard route). Various nondefault NBO options are
invoked by setting IOp(40)=1 in Overlay 6 (see Section
D.8.1) and including $NBO keylists in the usual way.
#ID.8.1 GAUSSIAN 90 sample input#N
0 A sample GAUSSIAN 90 input file to recreate the default
methylamine (RHF/321G at PopleGordon idealized geometry)
output displayed in Section A.3 is shown below:
# RHF/321G ExtraLinks=L607
Methylamine...RHF/321G//PopleGordon standard geometry
0 1
C
N 1 CN
H 1 CH 2 tet
H 1 CH 2 tet 3 120. 0
H 1 CH 2 tet 3 240. 0
H 2 NH 1 tet 3 60. 0
H 2 NH 1 tet 3 300. 0
CN 1.47
CH 1.09
NH 1.01
tet 109.4712
#T
@seg
0 #N(The $NBO keylist is not needed to perform the default
NBO analysis with GAUSSIAN 90.)
0 The following sample input file demonstrates how to select
nondefault options or analyses, such as the NLMO analysis
(Section B.6.2) and the dipole analysis (Section B.6.3):
# RHF/321G ExtraLinks=L607 IOp(6/40=1)
Methylamine...RHF/321G//PopleGordon standard geometry
0 1
C
N 1 CN
H 1 CH 2 tet
H 1 CH 2 tet 3 120. 0
H 1 CH 2 tet 3 240. 0
H 2 NH 1 tet 3 60. 0
H 2 NH 1 tet 3 300. 0
CN 1.47
CH 1.09
NH 1.01
tet 109.4712
$NBO NLMO DIPOLE $END
#T
@seg
0 #NNote that IOp(40) must be set to 1 whenever an $NBO
keylist is included in the GAUSSIAN 90 input file.
0 #NThe keylists of the NBO program should always appear at
the bottom of the GAUSSIAN 90 input file and should be
ordered: $NBO, $CORE, $CHOOSE, $DEL. NBO job options are
selected by inserting their associated keywords (Section
B.2) into the $NBO keylist. All NBO keywords are applicable
to the electronic wavefunctions computed by the GAUSSIAN 90
programs. It is advisable to terminate the GAUSSIAN 90
input file with a blank line.
0 If the NBO program encounters the endoffile while
searching for a keylist, the input file is rewound and the
search for the keylist is continued. This is particularly
useful for jobs which call the NBO analysis several times.
For example, an MP2 calculation with the GAUSSIAN 90 option
DENSITY=ALL causes Link 607 to loop over three densities
(SCF, Rho2, and MP2), and hence, the NBO analysis is called
three times, once for each density. A single $NBO keylist
(and $CORE and $CHOOSE keylists) will suffice as input for
all three analyses. Alternatively, separate $NBO keylists,
one for each density, could be inserted at the bottom of the
GAUSSIAN 90 input file.
0 The IOp parameters 4043 of Link 607 exert additional con
trol over the NBO program, as listed below:
#NBy default, the NBO analysis will be performed on the den
sity matrix for the current wavefunction. In general, it is
preferable to activate the DIPOLE and RESONANCE options by
keywords in the $NBO keylist rather than via the IOp parame
ters.
#ID.8.2 NBO energetic analysis#N
0 Due to the overlay structure of the GAUSSIAN 90 programs,
a nonstandard route must be employed to perform the NBO
energetic analysis. The following table lists and describes
the tasks of the GAUSSIAN 90 links in the order that they
appear in the nonstandard route:
#IDESCRIPTION#N
Perform the normal NBO analysis, storing information about
the NBOs for the NBO energetic analysis on the FILE48 direct
access file.
Read the next deletion listed in the $DEL keylist. If there
are no more deletions, move to the next link. Otherwise,
compute the modified density matrix, store it on the read
write files, and skip the next link in the nonstandard
route.
Finish GAUSSIAN 90 execution.
Using the modified density matrix, compute the deletion
energy by a single pass through the SCF energy evaluator.
Store the deletion energy on the readwrite files.
Read the deletion energy from the readwrite files and com
plete the energetic analysis. Step backwards, in the non
standard route, three links.
0 The following is a GAUSSIAN 90 input file that will gen
erate, in addition to the default NBO output, the NBO ener
getic (Section B.6.10) analysis of methylamine:
# NONSTD 1//1; 2//2; 3/5=5,11=1,25=14,30=1/1,2,3,11,14;
4/7=1/1; 5//1; 6/7=2,8=2,9=2,10=2,19=1,40=1/1,7;
6/40=2/7(1); 99/5=1,9=1/99; 5/7=1,13=1/1; 6/40=3/7(3);
Methylamine...RHF/321G//PopleGordon standard geometry
0 1
C
N 1 CN
H 1 CH 2 tet
H 1 CH 2 tet 3 120. 0
H 1 CH 2 tet 3 240. 0
H 2 NH 1 tet 3 60. 0
H 2 NH 1 tet 3 300. 0
CN 1.47
CH 1.09
NH 1.01
tet 109.4712
$NBO $END $DEL NOSTAR
ZERO 2 ATOM BLOCKS 4 BY 3
1 3 4 5
2 6 7
3 BY 4
2 6 7
1 3 4 5 $END
#T
@seg
0 #NNote that for the GAUSSIAN 90 version of the NBO pro
gram, each deletion in the $DEL keylist must begin on a new
line of the input file (the first deletion can follow the
``$DEL'' keylist identifier, as shown above). The ``$END''
keylist terminator must also appear on its own line.
#ID.8.3 Geometry reoptimization with NBO deletions#N
0 The structural effects of electron delocalization can be
examined by coupling the NBO energetic analysis to the
FletcherPowell (numerical) geometry optimization routines
of the GAUSSIAN 90 package. The following GAUSSIAN 90 input
file will reoptimize selected internal coordinates of
RHF/321G methylamine in the absence of its strong
#In#N#dN#u7arr gma #u*#d#d#
