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MathGroup Archive 2007

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Re: ndsolve ndsv problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79853] Re: ndsolve ndsv problem
  • From: chuck009 <dmilioto at comcast.com>
  • Date: Tue, 7 Aug 2007 01:25:40 -0400 (EDT)

I don't see where you're supplying the end points for the numeric calculations.  The code I wrote below just sets the boundary point at infinity at 1000 and does generate a solution which matches the two boundary points you supplied somewhat ok:

sol = NDSolve[0.0005635632304299039*psi[R] == 
     (2*Derivative[1][psi][R])/R + Derivative[2][psi][R] && 
    Derivative[1][psi][1] == 7.017487714753473 && 
    psi[1000] == 0, psi, {R, 1, 1000}, WorkingPrecision -> 30]
f[x_] := Evaluate[psi[x] /. Flatten[sol]]; 
Plot[f[x] /. Evaluate[Flatten[sol]], {x, 1, 100}]

In[146]:=
f[1000]
fd[x_] = D[f[x], x]
fd[1]

Out[146]=
\!\(0``40.78712463722495\)

Out[147]=
InterpolatingFunction[{{1.00000000000000000000000000000,1000.\
00000000000000000000000000}},<>][x]

Out[148]=
7.0324851897180024334773666



> Steps to reproduce:
> 1. Issue this command (given to you in InputFrom due
> to a copy/paste problem)
> 
> NDSolve[0.0005635632304299039*psi[R] ==
>    (2*Derivative[1][psi][R])/R +
>     Derivative[2][psi][R] &&
>   Derivative[1][psi][1] == 7.017487714753473 &&
>   psi[Infinity] == 0, psi, R]
>


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