The temperature of the sample in a resistance-heated diamond anvil cell is difficult to be measured directly and usually is calibrated by reading from the thermocouple attached to the diamond bevel. It is unclear how the temperature difference between the diamond bevel and the sample is affected by external factors such as thermal radiation and air convection. We performed a finite-element method simulation of the temperature field in the resistance-heated diamond anvil cell under different external conditions, and our simulations demonstrate that a thermal insulation cover of a low emissivity material and a unique double-layer structure can effectively reduce the temperature difference. Meanwhile, there is a non-negligible difference between the sample temperature at ambient pressure and that at high pressure when the diamond bevel has the same temperature. Some results of simulations have been confirmed by experiments using a designed double-layer cover.
It is unclear whether there is a liquid-liquid phase transition or not in the bismuth melt at high temperature and high pressure, if so, it is necessary to confirm the boundary of the liquid-liquid phase transition and clarify whether it is a first-order phase transition. Here based on X-ray absorption spectra and simulations, the temperature dependence of bismuth structures has been investigated under different pressures. According to the similarity of characteristic peaks of X-ray absorption near edge structure (XANES) spectra, we have estimated that the possible temperature ranges of liquid-liquid phase transition are 779 K ~ 799 K at 2.74 GPa and 859 K ~ 879 K at 2.78 GPa, 809 K ~ 819 K at 3.38 GPa and 829 K ~ 839 K at 3.39 GPa and 729 K ~ 739 K at 4.78 GPa, respectively. Using ab initio molecular dynamics (AIMD) simulations, we have obtained the stable structures of the bismuth melt at different temperatures and pressures and calculated their electronic structures. Meanwhile, two stable phases (phase III-like and phase IV-like) of bismuth melts are obtained from different initial phases of bismuth solids (phase III and phase IV) under the same condition (3.20 GPa and 800 K). Assuming that the bismuth melt undergoes a phase transition from IV-like to III-like between 809 K and 819 K at 3.38 GPa, the calculated electronic structures are consistent with XANES spectra, which provides a possible explanation for the first-order liquid-liquid phase transition.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.