AtomHybridizationVSEPRDescriptor.java

/*
 *  $RCSfile$
 *  $Author: egonw $
 *  $Date: 2007-02-07 23:20:44 +0100 (Wed, 07 Feb 2007) $
 *  $Revision: 7895 $
 *
 *  Copyright (C) 2004-2007  Miguel Rojas <miguel.rojas@uni-koeln.de>
 *
 *  Contact: cdk-devel@lists.sourceforge.net
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2.1
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 */
package org.openscience.cdk.qsar.descriptors.atomic;

import org.openscience.cdk.CDKConstants;
import org.openscience.cdk.config.AtomTypeFactory;
import org.openscience.cdk.exception.CDKException;
import org.openscience.cdk.interfaces.IAtom;
import org.openscience.cdk.interfaces.IAtomContainer;
import org.openscience.cdk.interfaces.IAtomType;
import org.openscience.cdk.qsar.DescriptorSpecification;
import org.openscience.cdk.qsar.DescriptorValue;
import org.openscience.cdk.qsar.IAtomicDescriptor;
import org.openscience.cdk.qsar.result.IntegerResult;
import org.openscience.cdk.tools.LoggingTool;

/**
 *  This class returns the hybridization of an atom.
 *
 *  <p>This class try to find a SIMPLE WAY the molecular geometry for following from
 *    Valence Shell Electron Pair Repulsion or VSEPR model and at the same time its
 *    hybridization of atoms in a molecule.
 *
 *  <p>The basic premise of the model is that the electrons are paired in a molecule 
 *    and that the molecule geometry is determined only by the repulsion between the pairs. 
 *    The geomtry adopted by a molecule is then the one in which the reulsions are minimized.
 *
 *  <p>It counts the number of electron pairs in the lewis dot diagram which
 *   are attached to an atom. Then uses the following table.
 * <pre>
 *    pairs on       hybridization 
 *    an atom              of the atom          geomtry             number for CDK.Constants
 *  ******************************************************************************************
 *      2                     sp                  linear                        1
 *      3                     sp^2            trigonal planarb                  2
 *      4                     sp^3              tetrahedral                     3
 *      5                     sp^3d         trigonal bipyramid                  4
 *      6                     sp^3d^2           octahedral                      5
 *      7                     sp^3d^3       pentagonal bipyramid                6
 *      8                     sp^3d^4        square antiprim                    7
 *      9                     sp^3d^5     tricapped trigonal prism              8
 * </pre>
 *
 *  <p>This table only works if the central atom is a p-block element 
 *   (groups IIA through VIIIA), not a transition metal.
 *
 *
 * <p>This descriptor uses these parameters:
 * <table border="1">
 *   <tr>
 *     <td>Name</td>
 *     <td>Default</td>
 *     <td>Description</td>
 *   </tr>
 *   <tr>
 *     <td></td>
 *     <td></td>
 *     <td>no parameters</td>
 *   </tr>
 * </table>
 *
 *@author         Miguel Rojas
 *@cdk.created    2005-03-24
 *@cdk.module     qsar
 *@cdk.set        qsar-descriptors
 * @cdk.dictref qsar-descriptors:atomHybridizationVSEPR
 */
00090 public class AtomHybridizationVSEPRDescriptor implements IAtomicDescriptor {

      org.openscience.cdk.interfaces.IAtom atom = null;
      private LoggingTool logger;
      private static AtomTypeFactory atomATF = null;
      
      /**
       *  Constructor for the AtomHybridizationVSEPRDescriptor object
       */
00099       public AtomHybridizationVSEPRDescriptor() {
            logger = new LoggingTool(this);
      }


      /**
       *  Gets the specification attribute of the AtomHybridizationVSEPRDescriptor object
       *
       *@return    The specification value
       */
00109       public DescriptorSpecification getSpecification() {
            return new DescriptorSpecification(
                        "http://www.blueobelisk.org/ontologies/chemoinformatics-algorithms/#atomHybridizationVSEPR",
                        this.getClass().getName(),
                        "$Id: AtomHybridizationVSEPRDescriptor.java 7895 2007-02-07 22:20:44Z egonw $",
                        "The Chemistry Development Kit");
      }


      /**
     * This descriptor does have any parameter.
     */
00121       public void setParameters(Object[] params) throws CDKException {
      }


      /**
       *  Gets the parameters attribute of the AtomHybridizationVSEPRDescriptor object
       *
       * @return    The parameters value
     * @see       #setParameters
       */
00131       public Object[] getParameters() {
            return null;
      }


      /**
       *  This method calculates the hybridization of an atom.
       *
       *@param  atom              The IAtom for which the DescriptorValue is requested
     *@param  container         Parameter is the atom container.
       *@return                   The hybridization
       *@exception  CDKException  Description of the Exception
       */

00145       public DescriptorValue calculate(IAtom atom, IAtomContainer container) throws CDKException
      {           
            IAtomType atomType = findMatchingAtomType(container, atom);
            
            double bondOrderSum = container.getBondOrderSum(atom);
            int charge = atom.getFormalCharge();
            int hcount = atom.getHydrogenCount();
            int valency = atomType.getValency();
            double nLonePair = (valency - ( hcount + bondOrderSum ) - charge) / 2;
            
            int hybridization = (int)nLonePair + ( hcount + container.getConnectedAtomsList(atom).size() );
            
            logger.debug("ATOM : bondOrderSum " + bondOrderSum + ", charge " + charge + ", hcount " + hcount + 
                         ", valency "  + valency + ", nLonePair " + nLonePair + ", hybridization "  + hybridization);
            
            int hybridizationCDK = 0;
            switch (hybridization) 
            {
                  case 2:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP1;break;
                  case 3:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP2;break;
                  case 4:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP3;break;
                  case 5:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP3D1;break;
                  case 6:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP3D2;break;
                  case 7:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP3D3;break;
                  case 8:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP3D4;break;
                  case 9:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_SP3D5;break;
                  default:
                        hybridizationCDK = CDKConstants.HYBRIDIZATION_UNSET;break;
            }

            return new DescriptorValue(getSpecification(), getParameterNames(), getParameters(), new IntegerResult(hybridizationCDK));
      }


      
      private IAtomType findMatchingAtomType(IAtomContainer container, org.openscience.cdk.interfaces.IAtom atom) throws CDKException 
      {
            try {
                  if(atomATF==null)
                        atomATF = AtomTypeFactory.getInstance("org/openscience/cdk/config/data/valency2_atomtypes.xml", 
            container.getBuilder());

                  // take atomtype for the given element...
                  IAtomType atomType = atomATF.getAtomType(atom.getSymbol());
                  return atomType;
                  
            } catch (Exception ex1) 
            {
                  logger.error(ex1.getMessage());
                  logger.debug(ex1);
                  throw new CDKException("Problems with AtomTypeFactory due to " + ex1.toString(), ex1);
            }
      }
      
      
      
      /**
       *  Gets the parameterNames attribute of the AtomHybridizationVSEPRDescriptor object
       *
       *@return    The parameterNames value
       */
00214       public String[] getParameterNames() {
        return new String[0];
      }


      /**
       *  Gets the parameterType attribute of the AtomHybridizationVSEPRDescriptor object
       *
       *@param  name  Description of the Parameter
     * @return       An Object of class equal to that of the parameter being requested
       */
00225       public Object getParameterType(String name) {
            String[] params = new String[1];
            params[0] = "targetPosition";
            return params;
      }
}