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The atomic-scale structure, melting curve, and equation of state of liquid gallium has been measured to high pressure (p) and high temperature (T) up to 26 GPa and 900 K by in situ synchrotron x-ray diffraction. Ab initio molecular dynamics simulations up to 33.4 GPa and 1000 K are in excellent agreement with the experimental measurements, providing detailed insight at the level of pair distribution functions. The results reveal an absence of dimeric bonding in the liquid state and a continuous increase in average coordination numbern Ga Ga from 10.4(2) at 0.1 GPa approaching ∼12 by 25 GPa. Topological cluster analysis of the simulation trajectories finds increasing fractions of fivefold symmetric and crystalline motifs at high p-T. Although the liquid progressively resembles a hard-sphere structure towards the melting curve, the deviation from this simple description remains large (≥40%) across all p-T space, with specific motifs of different geometries strongly correlating with low local two-body excess entropy at high p-T.

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2,3,5,6-Tetrachloropyridine (TCP) is an important chemical and intermediate for synthesis of pesticides and pharmaceuticals. The solubility of TCP in supercritical carbon dioxide was measured using a static analytical method at temperatures of 313 K, 323 K, and 333 K and pressures in the range of 10.0 MPa to 24.0 MPa. The result showed that TCP solubility increased with the increase of pressure at isothermal conditions, while it decreased with increasing temperature at isobaric conditions. The experimental data were correlated using four density-based models (Chrastil, Mendez-Santiago and Teja, Bartle, and Kumar and Johnston), respectively. The calculated results show good agreement with the experimental data.