Persistent Zero Linear Compressibility in γ‐PdCl ₂ over a Record‐Breaking Ultrawide Pressure Range

Abstract The “wine‐rack” negative linear compressibility (NLC) and zero linear compressibility (ZLC) mechanism plays an important role in current pressure‐induced anomalous compressibility (PIAC) researches, but is only defined in three‐dimensional (3D) structural materials. Here, the two‐dimensional (2D) layered “wine‐rack” ZLC mechanism is firstly proposed and rationalized in 2D structural materials, γ‐PdCl ₂ . The persistent ZLC along the c‐axis across an unprecedented pressure regime spanning 0 GPa to 80 GPa in γ‐PdCl ₂ is elaborated by employing first‐principles calculations. The competition between the compressive effect, due to intensified zigzag folding and interlayer van der Waals (vdWs) hardening, and the intrinsic expansive effect of hinging distortion of 2D “wine‐rack” frameworks brings negative ZLC (n‐ZLC) to positive ZLC (p‐ZLC) transition at about 1.3 GPa and p‐ZLC up to 80 GPa. A high‐pressure Pbcn phase of ɛ‐PdCl ₂ exhibiting ZLC (90–100 GPa) is verified. The phase transition at ∼85 GPa, induced by interlayer sliding, narrows the band gap via enhanced Pd‐Cl hybridization. This study pioneers the dimensional upgradation of the uniaxial “wine‐rack” PIAC mechanism from 3D to 2D, and further provides theoretical guidance for constructing one‐dimensional (1D) and zero‐dimensional (0D) “wine‐rack” systems, thereby accelerating the establishment of a comprehensive “wine‐rack” PIAC model applicable to all structural dimensions.