AIMPAC UTILITIES                                              bubble(1)

NAME
       Bubble - Finds critical points in del-squared rho.

SYNOPSIS
       Bubble dbtfile wfnfile

DESCRIPTION
       
       The program searches the surface of a sphere around the nucleus
       until a point is found with the desired curvatures. The location 	 
       of the critical point within this region is then found using a 	 
       Quasi-Newton method. The program then computes the values of 
       del-squared rho and Grad rho at the critical points.

ARGUMENTS

    dbtfile ( for example "hco2.dbt" )
       The dbtfile file contains the necessary information to perform 	 	 
       the search.

    wfnfile ( for example "hco2.wfn" )
       The wavefunction file contains the basis set and optimized 
       coefficients from a SCF calculation describing the charge 
       distribution of that molecule.

FORMAT

       The input to BUBBLE is free format with the first seven 	  	  
       characters of each card being ignored by the routine and used 
       by the user as labels for ease of use.  An example of the input 
       is given here.


          TITLE: O2 OF HCO2-,(3,-3)CRITICAL POINTS
          ATOM#:  2
          POINTS: 3
          SIGNAT: -3
          RANGE:  0.55 0.75

       The cards are used as follows;

   TITLE: O2 OF HCO2-,(3,-3)CRITICAL POINTS
          A 60 character title string.

   ATOM #: 2
          The atom number of the atom to be searched. 
                          
   POINTS: 3
          The number of critical points to be found.
          There are two choices which may be entered in this
          card.

             1. Enter the number of critical points expected.
             2. Enter 0 for a search for an unknown number of 
                critical points.

          The quickest route is to enter the number of critical points 	    
          that are expected in the neighbourhood of the searched atom. 
          The maximum number which can be entered in this card is 19.
 
          If the user has no idea of how many critical points are 	    	    
          present and cannot make an educated guess then entering a 0 
          in the card will have the program search for a length of time 
          and then print out all the points it has found. 

   SIGNAT: -3
          Enter the signature of the desired critical points which may 	    
          equal -3, -1, 1, or 3. Only critical points with the 
          indicated signature will be searched for. In the present 
          version of this program only one signature can be entered at 
          a time.

   RANGE: 0.55 0.75
          This card gives the minimum and maximum distances from the 	    	    
          nucleus to be searched. Both of these values must be positive 	    
          and the order of the two values in this card is important 
          (the first number must always be less than the second). The	 	    	    	
          critical points must lie between these two values so it is 	    	    
          important to have an approximate idea of how far the critical 	    
          points are from the nucleus. The length of time required to 	    	    
          find the critical points is proportional to the size of the 	    	    	
          searching interval. The raduis of the sphere on which the 	    	    
          critical points for a given quantum shell are found is 	    
          characteristic for each atom and are given in R. F. W. Bader: 	    
          'Atoms in Molecules-- A Quantum Theory', p.259, Clarendon 	    
          Press, Oxford (1990).


          Therefore the example shown above specifies a search around 
          the oxygen atom in the formate anion for three (3,-3) 
          critical points. The search will be restricted to the volume 
          enclosed by the radii of 0.55 au and 0.75 au from the oxygen 
          nucleus. As soon as three distinct (3,-3) critical points are 
          found the program will stop.

OUTPUT
          Bubble generates a file giving the locations and properties 
          of the critical points found. This file will have the file 
          extension '.bub'.

EXAMPLE
       bubble hco2 hco2
          This requests a search for critical points described
          in hco2.dbt using the wavefunction hco2.wfn.




Release 0.9                    AIMPAC                         bubble(1)