The explanation of heat is always the vibration of atoms. At absolute zero, the atoms stop vibrating and stand still. But what then vibrates? An atom consists of a very small positive nucleus surrounded by a negative cloud of electrons that may or may not be statistically located in certain places. When an electron absorbs a photon, it makes a quantum leap to a higher orbit and falls back to a lower orbit by re-emitting the photon. Is the vibration caused by these movements, with the electron cloud expanding and contracting? Or is there another effect?
Answer
Hi Robert,
Actually, the “vibration of atoms” is about storing energy. Since a proton is 1836 times heavier than an electron, you can also move it with a small difference in “motion” (in the quantum world nothing is really what it seems, so whether such an atomic nucleus really vibrates as you imagine just the question) can store a much greater energy than in the electrons. However, the vibration of atoms only has meaning if there are several in close proximity, such as in a molecule or crystal. If there is no external force field to make the atomic nucleus vibrate all around, then it will never change direction, but just move in a certain direction. So the vibrating of atoms is in fact the same phenomenon for the nucleus as what you describe for the electrons: adding an amount of energy to the nucleus, making it into a higher energy state (compared to one or more other nuclei nearby). These quanta of vibrational energy are smaller than those of electrons (typically this is the absorption of infrared radiation, as opposed to the more energetic UV for the electron transitions). And the electrons in this story, they move so fast that they can just follow regardless of the position of the nucleus and are just statistically located opposite the nucleus where they would be if the atom were not vibrating.
I hope that made it a bit clearer?
Answered by
prof. dr. Christophe Vande Velde
Thermal Analysis, Calorimetry, X-ray Crystallography, Organic Chemistry

Prinsstraat 13 2000 Antwerp
http://www.uantwerpen.be
.