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# tbgrad.h

    00001 //
    00002 // tbgrad.h --- definition of the abstract two-electron gradient builder
    00003 //
    00004 // Copyright (C) 1996 Limit Point Systems, Inc.
    00005 //
    00006 // Author: Edward Seidl <seidl@janed.com>
    00007 // Maintainer: LPS
    00008 //
    00009 // This file is part of the SC Toolkit.
    00010 //
    00011 // The SC Toolkit is free software; you can redistribute it and/or modify
    00012 // it under the terms of the GNU Library General Public License as published by
    00013 // the Free Software Foundation; either version 2, or (at your option)
    00014 // any later version.
    00015 //
    00016 // The SC Toolkit is distributed in the hope that it will be useful,
    00017 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00018 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00019 // GNU Library General Public License for more details.
    00020 //
    00021 // You should have received a copy of the GNU Library General Public License
    00022 // along with the SC Toolkit; see the file COPYING.LIB.  If not, write to
    00023 // the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
    00024 //
    00025 // The U.S. Government is granted a limited license as per AL 91-7.
    00026 //
    00027
    00028 #ifndef _chemistry_qc_scf_tbgrad_h
    00029 #define _chemistry_qc_scf_tbgrad_h
    00030
    00031 #ifdef __GNUC__
    00032 #pragma interface
    00033 #endif
    00034
    00035 #include <util/group/thread.h>
    00036
    00037 namespace sc {
    00038
    00039 template<class T>
    00040 class TBGrad : public Thread {
    00041   protected:
    00042     T& contribution;
    00043     double exchange_fraction;
    00044
    00045   public:
    00046     TBGrad(T&t, double ex = 1.0) : contribution(t), exchange_fraction(ex) {}
    00047     virtual ~TBGrad() {}
    00048
    00049     inline void set_scale(double& coulombscale, double& exchangescale,
    00050                           int i, int j, int k, int l) const
    00051     {
    00052       double scale = 1.0;
    00053
    00054       if ((i!=k)||(j!=l))
    00055         scale *= 2.0;
    00056
    00057       if (i!=j)
    00058         scale *= 2.0;
    00059
    00060       coulombscale = 0.5*scale;
    00061       exchangescale = -0.25*scale * exchange_fraction;
    00062
    00063       if (k!=l)
    00064         coulombscale *= 2.0;
    00065
    00066       if ((k!=l)&&(i==j))
    00067         exchangescale *= 2.0;
    00068     }
    00069 };
    00070
    00071 }
    00072
    00073 #endif
    00074
    00075 // Local Variables:
    00076 // mode: c++
    00077 // c-file-style: "ETS"
    00078 // End: