Bidirectional optimization of transport properties for thermoelectric performance via hydrostatic pressure in chalcopyrite Ag X Te 2 ( X = In , Ga )

Pressure tuning has emerged as a powerful strategy for manipulating the thermoelectric properties of materials by inducing structural and electronic modifications. Herein, we systematically investigate the transport properties and thermoelectric performance concerning lattice distortions induced by hydrostatic pressure in Ag-based chalcopyrite $\mathrm{Ag}X{\mathrm{Te}}₂$ $(X=\mathrm{In}, \mathrm{Ga})$. Our findings reveal that the lattice distortion in $\mathrm{Ag}X{\mathrm{Te}}₂$ exhibits distinct behaviors under lattice compression, diverging from trends observed at ambient pressure. Importantly, the hydrostatic pressure breaks the phenomenally negative correlation between thermal conductivity and lattice distortion. Pressure-induced softening of low-frequency acoustic phonons broadens the low-energy phonon spectrum, enhancing interactions between acoustic and optical phonons. Such broadening substantially increases the number of available three-phonon scattering channels, resulting in a marked reduction in thermal conductivity. Additionally, the applied pressure achieves a notable net increase in the power factor despite the strong coupling of electrical transport parameters, which underscores the potential for bidirectional optimization of transport properties in $\mathrm{Ag}X{\mathrm{Te}}₂$. As a result, the maximum ZT value of ${\mathrm{AgInTe}}₂$ is nearly doubled, demonstrating that pressure modulation is a powerful strategy for enhancing thermoelectric performance. Our work not only establishes the link between pressure, lattice dynamics, and thermoelectric properties within chalcopyrite $\mathrm{Ag}X{\mathrm{Te}}₂$, but also inspires the exploration of pressure-related optimization strategies for conventional thermoelectric materials.