Pressure–temperature phase diagrams of twelve materials relevant to diamond-anvil-cell research, on a shared log-pressure axis (10⁻⁴ → 10³ GPa). All boundaries are sourced from the literature; uncertain or contested features are drawn dashed and noted.
P (GPa, log) vs T (K). Filled fields are stable phases; lines are equilibrium boundaries.
Vector rendering — anchor values (triple points, transitions, critical points) verified against primary literature; smooth curves between anchors are Clapeyron-consistent interpolations, not new data.
How to read these diagrams
Pressure is on the vertical axis on a logarithmic scale (10⁻⁴ GPa ≈ 1 bar, up to 10³ GPa = 1 TPa), so transitions spanning bars to terapascals all fit on one chart. Temperature is linear on the horizontal axis (the range adapts to each material). Coloured regions are the thermodynamically stable phases; solid blue lines are melting / liquidus curves; dark-blue lines are solid–solid transitions; green dots mark triple points. The fields are drawn edge-to-edge (jointive tiling) so the boundaries are shared, not redrawn.
Method & reliability
Every transition pressure, triple point and melting curve is taken from peer-reviewed measurements or first-principles calculations, listed under "References" for each material. Dashed lines mark genuinely uncertain or contested features — extrapolations beyond data, the FeO "wüstite enigma", or hydrogen metallization (425 GPa Loubeyre vs 495 GPa Dias–Silvera). Smooth curves between anchor points are Clapeyron-consistent interpolations, not new data. Nothing contested is asserted as settled fact.
The twelve materials
H₂O ices & superionic · Fe α/γ/δ/ε/liquid (core) · C graphite/diamond · SiO₂ stishovite/seifertite · MgSiO₃ bridgmanite/post-perovskite · MgO periclase B1/B2 · NaCl halite B1/B2 (calibrant) · FeO wüstite · Si β-Sn/sh/hcp/fcc · Al fcc/hcp/bcc (TPa standard) · H₂ molecular/metallic · (Mg,Fe)SiO₃ spin crossover.