# I Numerical solution to the Schrodinger eqn. using Finite Difference Method

#### patrykh18

As part of my project I was asked to use the finite difference method to solve Schrodinger equation. I see how you can turn it into a matrix equation, but I don't know how to solve it if the energy eigenvalues are unknown. Are there any recommended methods I can use to determine those eigenvalues. Maybe for simplicity assume we are dealing with a finite square well and assume that for some reason you can't determine the energies in advance.

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#### stevendaryl

Staff Emeritus
As part of my project I was asked to use the finite difference method to solve Schrodinger equation. I see how you can turn it into a matrix equation, but I don't know how to solve it if the energy eigenvalues are unknown. Are there any recommended methods I can use to determine those eigenvalues. Maybe for simplicity assume we are dealing with a finite square well and assume that for some reason you can't determine the energies in advance.
Do you mean to numerically solve the Schrodinger equation? That does not directly lead to eigenvalues.

What you can do, although this is a lot of work, is to pick an energy, numerically solve the Schrodinger equation for the energy, and then look to see if the wave function blows up as $x \rightarrow \infty$. If so, try a slightly different energy. You've found an energy eigenvalue if the numerical solution of Schrodinger's equation leads to a wave function that is well-behaved at both $x=0$ and $x \rightarrow \infty$.

Actually, to solve Schrodinger's equation numerically, you need more than just the energy. You also need boundary conditions at $x=0$.

(The above is about the one-dimensional Schrodinger equation. In three-dimensions, you can often reduce the problem to a one-dimensional case if you have a spherically symmetric potential by using separation of variables.)

"Numerical solution to the Schrodinger eqn. using Finite Difference Method"

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