5 Distribution in frequency of the internal energy

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First click on calculate and double MC steps a few times to get good statistics for the density of modes.

The plot you see on the right is similar to the DOS plot. However, in place of the number of modes in each bin of the DOS histogram, it shows the internal energy associated with each of the frequency bins. The plots are shown for ten different temperatures up to the maximum value given by the Tmax slider. The area under any one of the curves is the internal energy of the crystal at the corresponding temperature. The area between two curves is the energy (heat) that must be added to the crystal to raise its temperature from the lower to the higher of the two temperatures.

Change Tmax to 10 K to see that, at low temperature, most of the thermal excitation energy of the crystal is associated with the low frequency modes.