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Infrared observations of the interstellar medium have unveiled the existence of numerous solid-phase molecules. The recent detection of uracil within the (162173) Ryugu asteroid has opened new prospects for the discovery of additional compounds, including nitrogenous bases, in the near future. To facilitate the comprehension, identification, and observation of these substances within astrophysical environments, precise measurements of their infrared band strengths are crucial. In this study, we present the outcomes of laboratory experiments conducted to investigate the behavior of adenine at various temperatures. The measured band strength from 3600 to 1970 cm−1 was determined to be 3.21⋅10−16 cm molecule−1. Additionally, as the temperature decreased, its behavior exhibited a well-fitted second-degree polynomial function. Notably, the experiments indicated no permanent phase changes or hysteresis during the cool-down and warm-up processes, further elucidating the thermal properties of adenine. [ABSTRACT FROM AUTHOR]

For CuInP2S6 layered crystal the temperature anomalies of the heat capacity and entropy at the ferrielectric ordering are explained based on the theoretical studies which predict the appearance of a critical endpoint and a bicritical endpoint on the phase diagram. Thus, the splitting of the anomaly of the heat capacity in Ag0.1Cu0.9InP2S6 mixed crystal can be interpreted as a transformation of the ferrielectric first-order phase transition, that is observed for CuInP2S6, into the sequent paraelectric–ferrielectric second-order phase transition and the isostructural first-order transition with a sharp change of the polarization in the ferrielectric phase. [ABSTRACT FROM AUTHOR]