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#include <iostream>
#include <algorithm>
#include <libint2.h>
#include <libint2/boys.h>
using namespace std;
using namespace libint2;
/** This function evaluates ERI over 4 primitive Gaussian shells.
See tests/eri/test.cc for an example of how to deal with
contracted Gaussians.
For simplicity, many details are omitted here, e.g. normalization.
*/
void
compute_eri(unsigned int am1, double alpha1, double A[3],
unsigned int am2, double alpha2, double B[3],
unsigned int am3, double alpha3, double C[3],
unsigned int am4, double alpha4, double D[3]
)
{
// I will assume that libint2_static_init() has been called elsewhere!
//-------------------------------------------------------------------------------------
// ------ the code in this section would usually be placed outside this function ------
// to occur once per calculation, not every time this function is called
// - allocate ERI evaluator object
Libint_eri_t erieval;
const unsigned int max_am = max(max(am1,am2),max(am3,am4));
libint2_init_eri(&erieval,max_am,0);
#if LIBINT_CONTRACTED_INTS
// if have support for contracted integrals, set the contraction length to 1
erieval.contrdepth = 1;
#endif
// - initialize Boys function evaluator
FmEval_Chebyshev7 fmeval(max_am);
//-------------------------------------------------------------------------------------
//
// Compute requisite data -- many of these quantities would be precomputed
// for all nonnegligible shell pairs somewhere else
//
const double gammap = alpha1 + alpha2;
const double Px = (alpha1*A[0] + alpha2*B[0])/gammap;
const double Py = (alpha1*A[1] + alpha2*B[1])/gammap;
const double Pz = (alpha1*A[2] + alpha2*B[2])/gammap;
const double PAx = Px - A[0];
const double PAy = Py - A[1];
const double PAz = Pz - A[2];
const double PBx = Px - B[0];
const double PBy = Py - B[1];
const double PBz = Pz - B[2];
const double AB2 = (A[0]-B[0])*(A[0]-B[0])
+ (A[1]-B[1])*(A[1]-B[1])
+ (A[2]-B[2])*(A[2]-B[2]);
erieval.PA_x[0] = PAx;
erieval.PA_y[0] = PAy;
erieval.PA_z[0] = PAz;
erieval.AB_x[0] = A[0] - B[0];
erieval.AB_y[0] = A[1] - B[1];
erieval.AB_z[0] = A[2] - B[2];
erieval.oo2z[0] = 0.5/gammap;
const double gammaq = alpha3 + alpha4;
const double gammapq = gammap*gammaq/(gammap+gammaq);
const double Qx = (alpha3*C[0] + alpha4*D[0])/gammaq;
const double Qy = (alpha3*C[1] + alpha4*D[1])/gammaq;
const double Qz = (alpha3*C[2] + alpha4*D[2])/gammaq;
const double QCx = Qx - C[0];
const double QCy = Qy - C[1];
const double QCz = Qz - C[2];
const double QDx = Qx - D[0];
const double QDy = Qy - D[1];
const double QDz = Qz - D[2];
const double CD2 = (C[0]-D[0])*(C[0]-D[0])
+ (C[1]-D[1])*(C[1]-D[1])
+ (C[2]-D[2])*(C[2]-D[2]);
erieval.QC_x[0] = QCx;
erieval.QC_y[0] = QCy;
erieval.QC_z[0] = QCz;
erieval.CD_x[0] = C[0] - D[0];
erieval.CD_y[0] = C[1] - D[1];
erieval.CD_z[0] = C[2] - D[2];
erieval.oo2e[0] = 0.5/gammaq;
const double PQx = Px - Qx;
const double PQy = Py - Qy;
const double PQz = Pz - Qz;
const double PQ2 = PQx*PQx + PQy*PQy + PQz*PQz;
const double Wx = (gammap*Px + gammaq*Qx)/(gammap+gammaq);
const double Wy = (gammap*Py + gammaq*Qy)/(gammap+gammaq);
const double Wz = (gammap*Pz + gammaq*Qz)/(gammap+gammaq);
erieval.WP_x[0] = Wx - Px;
erieval.WP_y[0] = Wy - Py;
erieval.WP_z[0] = Wz - Pz;
erieval.WQ_x[0] = Wx - Qx;
erieval.WQ_y[0] = Wy - Qy;
erieval.WQ_z[0] = Wz - Qz;
erieval.oo2ze[0] = 0.5/(gammap+gammaq);
erieval.roz[0] = gammapq/gammap;
erieval.roe[0] = gammapq/gammaq;
double K1 = exp(-alpha1*alpha2*AB2/gammap);
double K2 = exp(-alpha3*alpha4*CD2/gammaq);
double pfac = 2*pow(M_PI,2.5)*K1*K2/(gammap*gammaq*sqrt(gammap+gammaq));
//
// evaluate Boys function F_m for all m in [0,am]
//
unsigned int am = am1 + am2 + am3 + am4;
double* F = new double[am+1];
fmeval.eval(F, PQ2*gammapq, am);
// (00|00)^m = pfac * F_m
erieval.LIBINT_T_SS_EREP_SS(0)[0] = pfac*F[0];
erieval.LIBINT_T_SS_EREP_SS(1)[0] = pfac*F[1];
erieval.LIBINT_T_SS_EREP_SS(2)[0] = pfac*F[2];
erieval.LIBINT_T_SS_EREP_SS(3)[0] = pfac*F[3];
erieval.LIBINT_T_SS_EREP_SS(4)[0] = pfac*F[4];
// etc.
// compute ERIs
libint2_build_eri[am1][am2][am3][am4](&erieval);
// Print out the integrals
const double* eri_shell_set = erieval.targets[0];
const unsigned int n1 = (am1 + 1) * (am1 + 2)/2;
const unsigned int n2 = (am2 + 1) * (am2 + 2)/2;
const unsigned int n3 = (am3 + 1) * (am3 + 2)/2;
const unsigned int n4 = (am4 + 1) * (am4 + 2)/2;
for(int a=0; a<n1; a++) {
for(int b=0; b<n2; b++) {
for(int c=0; c<n3; c++) {
for(int d=0; d<n4; d++) {
cout << "a = " << a
<< "b = " << b
<< "c = " << c
<< "d = " << d
<< "(ab|cd) = " << *eri_shell_set;
++eri_shell_set;
}
}
}
}
// ------ like the code at the beginning, this usually goes outside this function ------
libint2_cleanup_eri(&erieval);
}
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