Posted by JW on February 26, 2014, 12:19 am, in reply to "Re: Normal modes of a 1D Chain"
Am I right to say that the sine is the acoustic mode and the cos is the optical mode?
"When you consider the monatomic chain you should get a dispersion omega ~ |sin(k a/4)|"
So when the 2 atoms are similar in the diatomic chain, you have essentially a monoatomic chain. But my confusion is that why do I have an optical mode when I treat m1=m2=m, do the math and get 2 solutions, but not when I consider the monoatomic chain directly (only the sine solution)?
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