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Energy from schrödinger equation

  1. Sep 23, 2011 #1

    i was currently thinking about this step here:

    [itex]\langle \psi_n, - \Delta \psi_n \rangle = \int |\nabla \psi_n|^2 dx [/itex]

    how do you get from the laplacian to this other expression?
  2. jcsd
  3. Sep 23, 2011 #2
    Integrate by parts to move a del operator from the right psi to the left one.
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