Program EFF-AO Version 1.0
                        --------------------------

                                I. Mayer 
            Chemical Research Center, Hungarian Academy of Sciences
                    H-1515 Budapest, P.O.Box 17, Hungary

             e-mail: mayer@chemres.hu

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   This program is one of the programs by I. Mayer and A. Hamza performing 
   *a posteriori* analysis of the ab initio wave wave functions produced by 
   the widely used "Gaussian" system G92, G94, G98, G03. 


   This version performs 

   A.)  BOND ORDER and VALENCE analysis (I. Mayer, Chem. Phys. Lett. 97, 270 
   1983; addendum for open shells: Chem. Phys. Lett. 117, 396, 1985, etc.);
   
   and

   B.)  Calculating the EFFECTIVE ATOMIC ORBITALS (orthogonal natural atomic 
   hybrids) diagonalizing the intraatomic block of the density matrix
   (R. McWeeny, Rev. Mod. Phys. 32, 335, 1960; see also I. Mayer, Chem. Phys. 
   Lett. 242, 499, 1995; J.Phys. Chem. 100, 6249, 1996).


   The program is applicable for both single determinant (SCF, DFT) and
   CORRELATED wave functions. (The DENSITY=CURRENT keyword should be used
   in the Gaussian run to get the correlated density matrix!)

   The only input of the program is the "formatted checkpoint file" 
   "Test.FChk" produced in a Gaussian run (keyword FormCheck).

   For other programs of the suite, also with energy partitioning
   schemes and "fyzzy atoms" analysis see the web-site

             http://occam.chemres.hu/programs



   This program uses routines from the program APOST by I. Mayer and
   A. Hamza - see the web-site indicated. 

   The basic bond order routine used here was written in 1982/83 by I. Mayer.
 
   




   Installation of the program:
   ---------------------------

   The "tar" file contains all the necessary FORTRAN source files as well
   as a "Makefile", which should be appropriate to produce the executable
   by issuing the command "make" on a UNIX or Linux system. (If necessary,
   replace the call to "f77" in the Makefile by the name of your FORTRAN
   compiler.) The name of the executable generated is "effao".

   Usage of the program:

   The only input required by the program is the "formatted checkpoint
   file" (Test.FChk) which is produced by the Gaussian, provided that the
   FormCheck keyword is included in the Gaussian input. In the program
   the file Test.FChk is used for input as the FORTRAN file fort.14,
   and is copied to file "Tmp" for actual processing (file fort.15).
 

   An alternative is to conserve the binary checkpoint file which is
   produced during the Gaussian run (include %chk="filename" in the input)
   and to format it by using the command "formchk" which is a part of the
   Gaussian system. The formatted checkpoint file should then be renamed
   (copied) to Test.Fchk (or to fort.14, if the statement
   "open(14,file='Test.FChk')" has been deleted from "subroutine input".
 

   A convenient way of using the program is to include it in the
   script performing the Gaussian run; one should take care of ensuring
   that "EFF-AO" should NOT start before Gaussian is finished. It is
   desirable to delete or rename the formatted checkpoint file Test.FChk
   after the calculation, in order to avoid its unwanted reuse.
 
   The "tar" file contains an example "Test.FChk" file and the respective
   "test-output" file (benzene HF/cc-pVTZ). It may happen that some of
   the orbitals are obtained with interchanged signs with respect to
   our example. 



   Cite this program as:

   I. Mayer, Program "EFF-AO", Version 1.0
   (Chemical Research Center, Hungarian Academy of Sciences),
   Budapest, 2008.
 
 

   Limitations:

   This version of the program is applicable up to 100 atoms,
   500 basis orbitals and 2000 primitive Gaussians.
   These numbers can easily be extended further by increasing
   every parameter, which is equal 100, 101, 500 or 2000.
   (Parameter maxat1 should be set equal "the value of maxat"+1.)

   Bugs etc.

   Please report bugs, problems etc. to the e-mail address above
   - we will try our best to help you.