double SpinAdapted::det_energy (const Slater& s)
{
// energy of a single slater determinant, used in truncation
double energy = 0;
Slater bra;
Slater ket;
for (int i = 0; i < s.size (); ++i)
{
ket = s;
bra = s;
energy += ket.trace (bra.d(i).c(i)) *
v_1 (i,i);
}
// diagonal
for (int i = 0; i < s.size (); ++i)
for (int j = 0; j < s.size (); ++j)
{
ket = s;
bra = s;
energy += .5 * ket.trace (bra.d(j).d(i).c(j).c(i))
* (v_2 (i,j,j,i) - v_2 (i,j,i,j));
}
return energy;
}
void SpinAdapted::Csf::applyRowminus(Csf& output, int irrep)
{
map<Slater, double>::iterator itout, it = det_rep.begin();
map<Slater, double> detsout;
for ( ; it!= det_rep.end(); it++)
for (int i=0; i<dmrginp.last_site(); i++) {
if (SymmetryOfSpatialOrb(i).getirrep() != irrep)
continue;
int I = dmrginp.spatial_to_spin()[i];
for (int j=0; j<2; j++) {
Slater s = (*it).first;
int sign = s.getSign();
s.d(I+2+j).c(I+j);
s.setSign(sign); //This is a hack.
if ( !s.isempty()) {
itout = detsout.find(s);
if (itout == detsout.end())
detsout[s] = (*it).second;
else
detsout[s] += (*it).second;
}
}
}
output.set_det_rep(detsout, S, IrrepVector(this->irrep.getirrep(), 0));
}
void SpinAdapted::Csf::applySminus(Csf& output)
{
map<Slater, double>::iterator itout, it = det_rep.begin();
map<Slater, double> detsout;
for ( ; it!= det_rep.end(); it++)
for (int i=0; i<Slater().size(); i+=2) {
Slater s = (*it).first;
s.d(i).c(i+1);
if ( !s.isempty()) {
itout = detsout.find(s);
if (itout == detsout.end())
detsout[s] = (*it).second;
else
detsout[s] += (*it).second;
}
}
output.set_det_rep(detsout, S, irrep);
output.set_S(S);
output.set_Sz(Sz-2);
output.set_n(n);
output.normalize();
}
