Alain Sepeda wrote:
my curiosity is raised by the Debye temperature, which seems to be the
minimum temperature for non-elastic phonons to transport heat...
Can someone explain us what is changing at Debye temperature ?
In order to tackle your question, let us first come to an agreement on what
the Debye Temperature[1] is. As far as I understand it, the Debye Temperature
can be thought of as roughly the temperature at which the very highest
frequency/energy phonon mode is excited in a material/crystal. Thus at/above
T(Debye), all possible Phonon Modes in the material/crystal are being excited,
thermally. In other words, if one wants to excite a material/crystal in every
possible way (in terms of The Debye Model), then raise the temperature of the
material/crystal above the Debye Temperature. I believe the Debye Temperature
for pure Nickel is roughly 450 K at/near Absolute Zero (I've seen values of 375
K, but that is the Temperature Dependent Phenomenological Debye Temperature as
one moves away from Absolute Zero towards Room Temperature and higher[2], and
the Debye Model is less accurate). So subtract 273.15 K and one obtains the
Debye Temperature of Nickel to be approximately 177 C, hence the value of 179 C
stated by John H during the demo. As one increases the temperature above the
Debye Temperature, the amplitudes of all the phonon vibrations/modes continue
to increase. I don't believe there is anything else really magical about the
Debye Temperature than this, but I could be wrong!
FYI: When Protium (Hydrogen-1) is incorporated into Nickel, the Debye
Temperature will change!
[1] Debye model --> http://en.wikipedia.org/wiki/Debye_model
[2] Lattice Mechanical Properties of Pd, Pt and Ni - A Model Potential Approach
-->
http://www.kps.or.kr/home/kor/journal/library/downloadPdf.asp?articleuid=%7B244F63AB-595B-4070-A7B7-6EB7FC293C68%7D
- Mark Jurich
