SCATTERH6                Library "JINRLIB"                       

    Author: O.Chuluunbaatar                                          You are
    Language: Fortran                                                
                                                                     visitor here.

           THE CALCULATIONS FOR A PHASE SHIFT AND WAVE FUNCTIONS
            OF THE SCHROEDINGER EQUATIONS FOR A ONE-DIMENSIONAL
                            SCATTERING PROBLEM

    The subroutine SCATTERH6 calculating a phase shift delta
    and wave functions Psi of the Schroedinger equations
               2
              d       2
          ( ------ + k  ) Psi(x) = V(x) * Psi(x)
                2
              dx
    with boundary conditions:

    Psi (x) -> 0 at x -> 0 or x ->   -infinity,
    Psi (x) -> sin(kx+delta) at x -> +infinity

    on a uniform grid by the Bode quadrature formula [1] with a given
    order of accuracy (from 2 up to 6) by the step h on a uniform grid.

    Structure:
    ---------- 
       Type:                                SUBROUTINE
       User Entry Names:                    SCATTERH6
       Internal Names:                      RSTEP XIVALUE1 PHI0
                                            PHI1 GAUSSJ MUU
       External References:                 POT,INITIAL - 
                                            user-supplied subprograms
    Usage:
    ------ 
    CALL SCATTERH6(DLAM1,PSI0,QQ,RMIN,RMAX,R,NN,IPOINT,EPS)

    The input datas: QQ, RMIN, RMAX, R, NN, IPOINTS, EPS, where:
       QQ            is given momentum;
       RMIN, RMAX    are minimal and maximal values of independent
                     variable R on a finite interval [RMIN, RMAX];
       R (I)         are nodes of a grid;
       NN            is number of subintervals;
       IPOINT        is number of nodes of the Bode quadrature formula
                     (from 2 up to 6);
       EPS           is given accuracy of a calculation process.

    Output datas: DLAM1, PSI0, where:
       DLAM1      is  value of a phase shift delta;
       PSI0 (I)   are values of a wave function Psi(R(I)).

    FUNCTION POT (R) is compounded by the user for calculation of
                     the potential function V(x).

    SUBROUTINE INITIAL (PSI0, DLAM0, QQ, R, IPOINT, N)
                     is compounded by the user for calculation of
                     asymptotic wave functions PSI0(1)...PSI0(IPOINT-1),
                     initial approximations: of wave functions
                     PSI0 (IPOINT)... PSI0 (N) and a phase shift DLAM0.

    Method:
    -------
    Algorithm, on the basis of which the given subroutine was constructed 
    described in [2-4]. The accuracy of calculation -
    up to O (h ^ (2 [(IPOINT+1) /2]). 

    Sources are submitted.

    References:
    -----------
        1. M. Abramowitz, I. Stegun, Handbook of mathematical
           functions, National Bureau of Standarts, NY, 1964.
        2. O. Chuluunbaatar, I.V. Puzynin, S.I. Vinitsky, Journal of
           Computational Methods in Sciences and Engineering, 2002, v.2, p.37.
        3. O. Chuluunbaatar, I.V. Puzynin, S.I. Vinitsky,
           JINR preprint P11-01-61, Dubna 2001.
        4. O. Chuluunbaatar, JINR abstract 11-2002-209, Dubna, 2002.