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#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
non-standard route).  Various non-default  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/3-21G  at Pople-Gordon idealized geometry)
output displayed in Section A.3 is shown below:

# RHF/3-21G ExtraLinks=L607

Methylamine...RHF/3-21G//Pople-Gordon 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
non-default  options  or analyses, such as the NLMO analysis
(Section B.6.2) and the dipole analysis (Section B.6.3):

# RHF/3-21G ExtraLinks=L607 IOp(6/40=1)

Methylamine...RHF/3-21G//Pople-Gordon 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  end-of-file  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 40-43 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  non-standard  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 non-standard 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 non-standard
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 read-write files.

Read the deletion energy from the read-write 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/3-21G//Pople-Gordon 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
Fletcher-Powell (numerical) geometry  optimization  routines
of the GAUSSIAN 90 package.  The following GAUSSIAN 90 input
file  will  reoptimize  selected  internal  coordinates   of
RHF/3-21G   methylamine   in   the  absence  of  its  strong
#In#N#dN#u7arr gma  #u*#d#d#
  
Modified: Tue Jul 11 16:00:00 1995 GMT
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