New thermal conductivity mechanism in triclinic 4-bromobenzophenone crystal

Anomalous behavior of thermal conductivity at high temperatures for molecular crystals composed of flexible molecules

“…1 and 2). The normal behavior is mainly governed by phonon -phonon scattering and the anomalous changes are attributed to a new mechanism of heat transfer by high-energy excitations [11].…”

“…can be neglected. The extensive experimental evidence currently available on isochoric and isobaric thermal conductivities of molecular crystals shows that the dependence κ(T) is also influenced by crystal lattice anharmonicities [2] and intensive hybridization (coupling) of acoustic phonons and low-frequency optical excitations (e.g., see [3][4][5][6][7][8][9][10][11][12][13]). It has been found that for many molecular crystals the high-temperature thermal conductivity can be approximated as a sum of two terms κ(T) = А/Т + В, where A/T refers to the effect of propagating phonons (Eucken law) and В = const refers to an additional temperatureindependent contribution of localized or diffusive short-wavelength vibrational modes.…”

“…Under a temperature gradient, the flow of such energy states are highly temperature dependent and the dependence increases with increasing the number of excited states migrating between the neighboring molecules. The new type of heat transfer was detected in a single crystal of parabromobenzophenone (4-BrBP C13H9BrO) [11]. Such a contribution to the total thermal conductivity can be described by the Arrhenius equation: κТА(Т) = κ0 ехр(-Е/kBТ), where E is the activation energy and κ0 is the pre -exponential factor characterizing the intensity of the thermally activated heat transfer.…”

Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C4H9NH3)2CuCl4

“…Recently, the thermal conductance of several molecular crystals has been measured by using instruments that can accommodate sub‐millimeter samples . These measurements demonstrated anomalous thermal conductance behavior in the crystals of fullerenes, 4‐bromobenzophenone, and substituted benzenes . These crystals show transitions from a static to a rotational phase, which is considered to be a mesophase between the anisotropic crystals and an isotropic liquid.…”

“…[1][2][3][4][5][6][7][8][9][10] These measurements demonstrated anomalous thermal conductanceb ehavior in the crystalso ff ullerenes, 4-bromobenzophenone, and substituted benzenes. [11][12][13] These crystals show transitions from as tatic to ar otational phase, which is considered to be am esophase between the anisotropic crystalsa nd an isotropic liquid.…”