Fizika Nizkikh Temperatur: Volume 46, Number 11 (November 2020), p. 1331-1335 ( to contents , go back )
Negative thermal expansion in solid deuteromethane
Yu. A. Freiman and V. V. Vengerovsky
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine Kharkiv 61103, Ukraine
A. F. Goncharov
Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW Washington D.C. 20015, USA
Received 23 August, 2020, published online September 21, 2020
The thermal expansion at constant pressure of solid CD4 III is calculated for the low-temperature region where only the rotational tunneling modes are essential and the effect of phonons and librons can be neglected. It is found that in mK region there is a giant peak of the negative thermal expansion. The height of this peak is comparable or even exceeds the thermal expansion of solid N2, CO, O2, or CH4 in their triple points. It is shown that like in the case of light methane, the effect of pressure is quite unusual: as evidenced from the pressure dependence of the thermodynamic Grüneisen parameter (which is negative and large in the absolute value), solid CD4 becomes increasingly quantum with rising pressure.
Key words: solid deuteromethane, negative thermal expansion, Grüneisen thermodynamical parameter.