/* gover.f -- translated by f2c (version 19950314).
   You must link the resulting object file with the libraries:
	-lF77 -lI77 -lm   (in that order)
*/

#include "f2c.h"

/* Common Block Declarations */

struct {
    char argz[512];
} argz_;

#define argz_1 argz_

struct {
    integer nztype[107], mtype[30], ltype;
} natype_;

#define natype_1 natype_

struct {
    doublereal c[360]	/* was [60][6] */, z[360]	/* was [60][6] */;
} temp_;

#define temp_1 temp_

struct {
    integer natorb[107];
} natorb_;

#define natorb_1 natorb_

/* Subroutine */ int gover_(integer *ni, integer *nj, doublereal *xi, 
	doublereal *xj, doublereal *r, doublereal *sg)
{
    /* Initialized data */

    static integer ngauss = 6;

    /* System generated locals */
    integer i__1, i__2, i__3, i__4;
    doublereal d__1, d__2;

    /* Builtin functions */
    double sqrt(doublereal), exp(doublereal);

    /* Local variables */
    static doublereal tomb;
    static integer i, j, k, l;
    static doublereal s[36]	/* was [6][6] */;
    static integer ka, kb, is;
    static doublereal adb;
    static integer ifa, ifb;
    static doublereal amb, apb, abn;
    static integer ila, ilb, nat, nbt;

/* ***********************************************************************
 */
/*                                                                      * 
*/
/*   GOVER CALCULATES THE OVERLAP INTEGRALS USING A GAUSSIAN EXPANSION  * 
*/
/*         STO-6G BY R.F. STEWART, J. CHEM. PHYS., 52 431-438, 1970     * 
*/
/*                                                                      * 
*/
/*         ON INPUT   NI   =  ATOMIC NUMBER OF FIRST ATOM               * 
*/
/*                    NJ   =  ATOMIC NUMBER OF SECOND ATOM              * 
*/
/*                    R    =  INTERATOMIC DISTANCE IN ANGSTROMS         * 
*/
/*         ON EXIT    S    =  9X9 ARRAY OF OVERLAPS, IN ORDER S,PX,PY,  * 
*/
/*                            PZ                                        * 
*/
/*                                                                      * 
*/
/* ***********************************************************************
 */
/* COMDECK SIZES */
/************************************************************************
****/
/*  THIS FILE CONTAINS ALL THE ARRAY SIZES FOR USE IN MOPAC.              
**/
/*                                                                        
**/
/*    THERE ARE ONLY  PARAMETERS THAT THE PROGRAMMER NEED SET:            
**/
/*    MAXHEV = MAXIMUM NUMBER OF HEAVY ATOMS (HEAVY: NON-HYDROGEN ATOMS)  
**/
/*    MAXLIT = MAXIMUM NUMBER OF HYDROGEN ATOMS.                          
**/
/*    MAXTIM = DEFAULT TIME FOR A JOB. (SECONDS)                          
**/
/*    MAXDMP = DEFAULT TIME FOR AUTOMATIC RESTART FILE GENERATION (SECS)  
**/
/*                                                                        
**/
/*                                                                        
**/
/************************************************************************
****/
/*                                                                        
**/
/*  THE FOLLOWING CODE DOES NOT NEED TO BE ALTERED BY THE PROGRAMMER      
**/
/*                                                                        
**/
/************************************************************************
****/
/*                                                                        
**/
/*   ALL OTHER PARAMETERS ARE DERIVED FUNCTIONS OF THESE TWO PARAMETERS   
**/
/*                                                                        
**/
/*     NAME                   DEFINITION                                  
**/
/*    NUMATM         MAXIMUM NUMBER OF ATOMS ALLOWED.                     
**/
/*    MAXORB         MAXIMUM NUMBER OF ORBITALS ALLOWED.                  
**/
/*    MAXPAR         MAXIMUM NUMBER OF PARAMETERS FOR OPTIMISATION.       
**/
/*    N2ELEC         MAXIMUM NUMBER OF TWO ELECTRON INTEGRALS ALLOWED.    
**/
/*    MPACK          AREA OF LOWER HALF TRIANGLE OF DENSITY MATRIX.       
**/
/*    MORB2          SQUARE OF THE MAXIMUM NUMBER OF ORBITALS ALLOWED.    
**/
/*    MAXHES         AREA OF HESSIAN MATRIX                               
**/
/************************************************************************
****/
/************************************************************************
****/
/*  FOR SHORT VERSION USE LINE WITH NMECI=1, FOR LONG VERSION USE LINE    
**/
/*  WITH NMECI=10                                                         
**/
/************************************************************************
****/
/*     PARAMETER (NMECI=1,   NPULAY=1) */
/************************************************************************
****/
/* DECK MOPAC */
/* next line added for Unix implementation for command line arguments */

    /* Parameter adjustments */
    sg -= 10;
    --xj;
    --xi;

    /* Function Body */

/*    FIND START AND END OF GAUSSIAN */

    ifa = (natype_1.nztype[*ni - 1] << 2) - 3;
    if (temp_1.c[ifa] != 0.) {
	ila = ifa + 3;
    } else {
	ila = ifa;
    }
    ifb = (natype_1.nztype[*nj - 1] << 2) - 3;
    if (temp_1.c[ifb] != 0.) {
	ilb = ifb + 3;
    } else {
	ilb = ifb;
    }

/*  CONVERT R INTO AU */

    *r /= .529167;
/* Computing 2nd power */
    d__1 = *r;
    *r = d__1 * d__1;
    ka = 0;
    i__1 = ila;
    for (i = ifa; i <= i__1; ++i) {
	++ka;
	nat = ka - 1;
	kb = 0;
	i__2 = ilb;
	for (j = ifb; j <= i__2; ++j) {
	    ++kb;
	    nbt = kb - 1;

/*         DECIDE IS IT AN S-S, S-P, P-S, OR P-P OVERLAP */

	    if (nat > 0 && nbt > 0) {
/*    P-P */
		is = 4;
		tomb = (xi[nat] - xj[nat]) * (xi[nbt] - xj[nbt]) * 
			3.5711928576;
	    } else if (nat > 0) {
/*    P-S */
		is = 3;
		tomb = (xi[nat] - xj[nat]) * 1.88976;
	    } else if (nbt > 0) {
/*    S-P */
		is = 2;
		tomb = (xi[nbt] - xj[nbt]) * 1.88976;
	    } else {
/*    S-S */
		is = 1;
	    }
	    i__3 = ngauss;
	    for (k = 1; k <= i__3; ++k) {
		i__4 = ngauss;
		for (l = 1; l <= i__4; ++l) {
		    s[k + l * 6 - 7] = 0.;
		    amb = temp_1.z[i + k * 60 - 61] + temp_1.z[j + l * 60 - 
			    61];
		    apb = temp_1.z[i + k * 60 - 61] * temp_1.z[j + l * 60 - 
			    61];
		    adb = apb / amb;

/*           CHECK OF OVERLAP IS NON-ZERO BEFORE STARTING 
*/

		    if (adb * *r < 90.) {
			abn = 1.;
			switch (is) {
			    case 1:  goto L50;
			    case 2:  goto L10;
			    case 3:  goto L20;
			    case 4:  goto L30;
			}
L10:
			abn = tomb * 2.f * temp_1.z[i + k * 60 - 61] * sqrt(
				temp_1.z[j + l * 60 - 61]) / amb;
			goto L50;
L20:
			abn = tomb * -2.f * temp_1.z[j + l * 60 - 61] * sqrt(
				temp_1.z[i + k * 60 - 61]) / amb;
			goto L50;
L30:
			abn = -adb * tomb;
			if (nat == nbt) {
			    abn += .5;
			}
/* L40: */
			abn = abn * 4. * sqrt(apb) / amb;
L50:
/* Computing 3rd power */
			d__1 = sqrt(apb) * 2.f / amb, d__2 = d__1;
			s[k + l * 6 - 7] = sqrt(d__2 * (d__1 * d__1)) * exp(
				-adb * *r) * abn;
		    }
/* L60: */
		}
	    }
	    sg[ka + kb * 9] = 0.;
	    i__4 = ngauss;
	    for (k = 1; k <= i__4; ++k) {
		i__3 = ngauss;
		for (l = 1; l <= i__3; ++l) {
/* L70: */
		    sg[ka + kb * 9] += s[k + l * 6 - 7] * temp_1.c[i + k * 60 
			    - 61] * temp_1.c[j + l * 60 - 61];
		}
	    }
/* L80: */
	}
    }
    return 0;
} /* gover_ */