CODESSA 2.7.10 - Using Gaussian Data with CODESSA

     Authors:  Alan Katritsky, Mati Karelson, Victor S. Lobanov, 
               Roy Dennington and Todd Keith
     Copyright (c) 1994-1995 by University of Florida
     Portions Copyright (c) 1996-2007 by Semichem, Inc.
     All Rights Reserved
     Redistribution or resale, except by Semichem, Inc., is prohibited.    

Among the new features added to Codessa is the ability to obtain
molecular structures and corresponding Codessa descriptors from 
Gaussian (development and testing was based on g94 and g98 and g03) output (.log) 
files.  The procedure for using Gaussian-based structures and descriptors
in Codessa is similar to the AMPAC-based procedure (see the Codessa-2.7.10
manuals and the *.readme files for detailed information on the use of
Codessa).  There are some differences between AMPAC-based and Gaussian-
based Codessa, however, and these are outlined below.

1)  To obtain molecular structures and most of the necessary quantum-
    chemical descriptor information for Codessa, the keywords 
    "Pop=(Regular, NBORead)" and "Density=Current" should be used in 
    the route section of the Gaussian input (.com or .gjf) file and one should
    specify #P to start the route section and one should add the NBO 
    control line "$NBO BNDIDX $END" after the blank line following the 
    molecule specification section of the .com or .gjf file.  If vibrational 
    frequencies, thermodynamic, polarizability and related descriptors 
    are desired then one should specify the keyword "Freq" in the route
    section.  Here are some samples:

    ***********************************************************
    %chk=h2o.chk
    #P HF/6-31G* Opt Freq Pop=(Regular,NBORead) Density=Current

    H2O

    0 1
    O
    H 1 OH
    H 1 OH 2 HOH

    OH 1.0
    HOH 105.0

    $NBO BNDIDX $END
    ***********************************************************

    ...
    #P MP2/6-31G* Opt Freq Pop=(Regular,NBORead) Density=Current
    ...
    $NBO BNDIDX $END

    ...
    #P B3LYP/6-31G* Opt Freq Pop=(Regular,NBORead) Density=Current
    ...
    $NBO BNDIDX $END

    Note that the use of "Density=Current" is necessary for post-SCF
    methods such as MP2, so that that post-SCF density is used for the
    NAO/NBO analysis instead of just the default SCF density.

    Most other Gaussian keywords may also be specified in the route
    section of a .com or .gjf file without affecting the use of Codessa with 
    the corresponding .log file.  There are some exceptions, however.

    See 4) below for automatic modification of Gaussian input files for
    use with Codessa.

2)  Instead of using the two column-header keywords AMPSCFPATHS and 
    AMPTHERMOPATHS in a Codessa input file, one may use the single
    keyword GAUSSSCFPATHS (or the single keyword GAUSSTHERMOPATHS) to
    specify the Gaussian .log file containing all of the descriptor data
    (including "quantum-chemical" and "thermodynamic") for each particular
    structure.  For example,

    STRNAME               PROPVALUES:bp  GAUSSSCFPATHS     
    "3-chloropropene"     318.11         gauss/bp004.log  
    "1,3-butadiene"       268.74         gauss/bp025.log  
    "isoprene"            307.21         gauss/bp060.log  
    "benzene"             353.24         gauss/bp089.log  
    "cyclohexane"         353.87         gauss/bp098.log  
    "n-hexane"            341.88         gauss/bp119.log  
    "m-xylene"            412.27         gauss/bp145.log  
    "3,3-diethylpentane"  419.34         gauss/bp180.log  

    It is NOT necessary to specify separate "SCF" and "THERMO" Gaussian
    .log files to have Codessa read in all of the possible descriptors,
    IF all of the descriptor information for a particular structure is
    in one .log file.  If, however, the "thermodynamic" data is in a
    separate .log file (one generated without Pop=(Regular,NBO)) then
    one may specify this with the column-header keyword GAUSSTHERMOPATHS.
    For example,

    STRNAME               PROPVALUES:bp  GAUSSSCFPATHS     GAUSSTHERMOPATHS   
    "3-chloropropene"     318.11         gauss/bp004.log   gauss/bp004_t.log
    "1,3-butadiene"       268.74         gauss/bp025.log   gauss/bp025_t.log
    "isoprene"            307.21         gauss/bp060.log   gauss/bp060_t.log
    "benzene"             353.24         gauss/bp089.log   gauss/bp089_t.log
    "cyclohexane"         353.87         gauss/bp098.log   gauss/bp098_t.log
    "n-hexane"            341.88         gauss/bp119.log   gauss/bp119_t.log
    "m-xylene"            412.27         gauss/bp145.log   gauss/bp145_t.log
    "3,3-diethylpentane"  419.34         gauss/bp180.log   gauss/bp180_t.log

    Note that the keywords GAUSSSCFPATHS and GAUSSTHERMOPATHS do NOT imply
    that one is restricted to SCF methods only in using Gaussian-based
    Codessa.  For example, MP2 and DFT may be used, as shown above.

3)  There are currently a few quantum-chemical descriptors which are
    obtainable from AMPAC output but not from Gaussian output.  These are
    the Heat of Formation, the GAMMA Hyperpolarizability and the some of the
    "energy-partitioning descriptors", such as the "Max resonance energy"
    or "Min e-e repulsion" for a given atom type.  The Beta
    Hyperpolarizability is NOT available for DFT methods and post_SCF 
    methods by default when running a "Freq" calculation.  In addition,
    some of the Gaussian-based descriptors are defined differently than
    the corresponding AMPAC-based ones.  For example, the bond-orders and 
    atomic valencies are defined in terms of the Wiberg bond-index matrix 
    using Natural Atomic Orbitals.