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Re: Quantum Mechanics, Boundary Value Problem

Rob Knapp has written some examples of Schrodinger's equation. Try searching
conference proceedings in the information centre.


On 22/7/04 5:34 PM, in article cdnqm4$l7t$1 at, "anthony danese"
<danese at> wrote:

> Hi,
> I'm trying to find a numerical solution to Schrodinger's equation for
> a nearly free electron potential (V(x)=Cos(x)) which meets an image
> potential which is of the form (V(x)=C - 1/x) where C is a constant.
> I can set up the problem using NDSolve, with 2 of my boundary
> conditions being continuity of the wave function (psi) and its
> derivative(psi') where the 2 potentials meet.  The problem is that I
> need 2 other boundary conditions--I attempt to arbitrarily set psi = 0
> far into the Cos(x)-like region of the potential and I would like psi
> to vanish as for large values of x in the C-1/x region of space.  When
> I try to run NDSolve, I either get the trivial psi = 0 or I get an
> error telling me that the boundary conditions are not well defined.
> As a test, I have tried to run NDSolve to find psi for a step
> potential where the step potential is greater than the energy of the
> electron.  The solution should be free electron-like away from the
> step and the solution should decay into the step.  This is a problem
> that is easily solved analytically but Mathematica doesn't like the
> way I'm stating the boundary conditions.  Is there anyway to solve
> these particular examples of Schrodinger's equation with NDSolve?
> Any help would be greatly appreciated,
> anthony danese

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