Calibration of local chemical pressure by optical probe

Chemical stabilization of a high-pressure metastable state is a major challenge for the development of advanced materials. Although chemical pressure (P(chem)) can effectively simulate the effect of physical pressure (P(phy)), experimental calibration of the pressure passed to local structural motifs, denoted as local chemical pressure (P(chem-)(Δ)) which significantly governs the function of solid materials, remains absent due to the challenge of probing techniques. Here we establish an innovative methodology to experimentally calibrate the P(chem-)(Δ) and build a bridge between P(chem) and P(phy) via an optical probe strategy. Site-selective Bi(3+)-traced REVO(4) (RE = Y, Gd) is adopted as a prototype to introduce Bi(3+) optical probes and on-site sense of the P(chem-)(Δ) experienced by the REO(8) motif. The cell compression of RE(0.98)Bi(0.02)VO(4) under P(phy) is chemically simulated by smaller-ion substitution (Sc(3+) → RE(3+)) in RE(0.98-)(x)Sc(x)Bi(0.02)VO(4). The consistent red shift (Δλ) of the emission spectra of Bi(3+), which is dominated by locally pressure-induced REO(8) dodecahedral variation in RE(0.98)Bi(0.02)VO(4) (P(phy)) and RE(0.98-)(x)Sc(x)Bi(0.02)VO(4) (P(chem-)(Δ)), respectively, is evidence of their similar pressure-dependent local structure evolution. This innovative Δλ-based experimental calibration of P(chem-)(Δ) in the crystal-field dimension portrays the anisotropic transmission of P(chem) to the local structure and builds a bridge between P(chem-)(Δ) and P(phy) to guide a new perspective for affordable and practical interception of metastable states.