Ionic structure, liquid-liquid phase transitions, x-ray diffraction, and x-ray Thomson scattering in shock-compressed liquid silicon in the 100-200 GPa regime

Journal article

Recent cutting-edge experiments have provided in situ structure characterization and measurements of the pressure (P), density (¯ρ) and temperature (T) of shock compressed silicon in the 100 GPa range of pressures and up to ∼10,000K. We present first-principles calculations in this P, T, ρ¯ regime to reveal a plethora of novel liquid-liquid phase transitions (LPTs) identifiable via discontinuities in the pressure and the compressibility. Evidence for the presence of a highly-correlated liquid (CL) phase, as well as a normal-liquid (NL) phase at the LPTs is presented by a detailed study of one LPT. The LPTs make the interpretation of these experiments more challenging. The LPTs preserve the short-ranged ionic structure of the fluid by collective adjustments of many distant atoms when subject to compression and heating, with minimal change in the ion-ion pair-distribution functions, and in transport properties such as the electrical and thermal conductivities σ and κ. We match the experimental X-Ray Thomson scattering and X-ray diffraction data theoretically, and provide pressure isotherms, ionization data and compressibilities that support the above picture of liquid silicon as a highly complex LPT-driven “glassy” metallic liquid. These novel results are relevant to materials research, studies of planetary interiors, high-energy-density physics, and in laser-fusion studies.

Authors: Dharma-wardana, MWC; Klug, DD; Poole, H; Gregori, G

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review E
• Volume: 111
• Issue: 1
• Article number: 015205
• Publication date: 2025-01-14
• Acceptance date: 2024-12-23
• DOI: 10.1103/PhysRevE.111.015205
• EISSN: 2470-0053
• ISSN: 2470-0045
• Language: English