l20 - Multiple atoms and bands Electron momentum and bands...

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Multiple atoms and bands Electron momentum and bands Metals and insulators Semiconductors Diodes: p - n junctions Diode circuits Transistors Some course stuff I’m not quite done grading exam 2 yet . . . Thursday, I hope. Book report: I’ve now opened it on SafeAssign in Blackboard. All submissions should be through SafeAssign, rather than by printed report. The deadline for submitting it on Blackboard is 11 pm on Sunday, December 6. You have lots of time to get it done; no exceptions for late hand-ins. What should the book report cover? It should give me an idea of what the book was about, though your paper should not consist entirely of a summary of the book. It should give me an idea of what you learned about a subject in modern physics that is different from what you learned from the course textbook, lectures, homework, and exams. You might discuss interesting questions that the book report raises in your mind. You should strive to make it interesting and stimulating. It should show me how you are actively engaged in thinking about modern physics. It should use correct spelling and grammar.
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Multiple atoms and bands Electron momentum and bands Metals and insulators Semiconductors Diodes: p - n junctions Diode circuits Transistors More than one atom What happens when you bring two atoms near to each other? It depends on the sign of ψ (see Serway Fig. 11.7, 12.17; these figures are from Krane):
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Multiple atoms and bands Electron momentum and bands Metals and insulators Semiconductors Diodes: p - n junctions Diode circuits Transistors Energy potential for H 2 Consider the energy terms versus separation distance for symmetric and antisymmetric wavefunctions in H 2 : U P is the repulsive Coulomb potential between nuclei. E + is for ψ 1 + ψ 2 . In this case the strongest binding is when the two atoms overlap, because the 1 s state is happy to hold two electrons. In this limit we effectively have Z = 2 and a binding energy of E = 13 . 6 eV ( Z = 2 ) 2 ( n = 1 ) 2 or -54.4 eV E is for ψ 1 ψ 2 . In this case the wavefunction has a zero at small r , which is more like a 2 p state than a 1 s state. Therefore the energy goes more like E = 13 . 6 eV ( Z = 2 ) 2 ( n = 2 ) 2 or -13.6 eV Adding either U P + E + , or U P + E , gives two different relationships between binding energy and separation distance.
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bands Electron momentum and bands Metals and insulators Semiconductors Diodes: p - n junctions Diode circuits Transistors H 2 energy II Again, the energy terms are U P for Coulomb potential between nuclei E + for ψ 1 + ψ 2 . E
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l20 - Multiple atoms and bands Electron momentum and bands...

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