CdTe undergoes a pressure-induced phase transformation from the zinc-blende ($B3$) to the rock-salt ($B1$) structure in the pressure range of $2-4\mathrm{G}\mathrm{Pa}$. However, at temperatures below $773\mathrm{K}$, powder-diffraction experiments further have established a narrow pressure range in which an intermediate cinnabar phase exists although the transformation mechanisms remain unclear. Ab initio metadynamics simulations are performed to examine the pressure-induced $B3\text{−}B1$ phase transformation of CdTe close to the experimental transition pressure at room temperature. The transformation upon compression into the rock-salt phase is proceeded by parallel sliding of alternating ${\left\{111\right\}}_{B3}$ planes along a ${\langle 110\rangle }_{B3}$ direction relative to in-between stationary ${\left\{111\right\}}_{B3}$ planes. This sliding mechanism produces shearing of the six-membered rings of the zinc-blende phase resulting in the brief formation of a five-coordinated structure before the transformation into the six-coordinated rock-salt phase is complete. A similar, albeit reversed, transformation mechanism is observed upon decompression starting from the rock-salt phase. The observed transformation mechanism exhibits an orientation relationship between one of the three-fold axes of the cubic phases as found experimentally. Significantly, an intermediate cinnabar phase is not observed in the simulated phase transformation, contrary to expectations from diffraction experiments. Accordingly, the phase stability for the experimentally proposed cinnabar structure of CdTe and the pressure dependence of its structural, mechanical, and electrical properties are investigated.

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• Chemical bonding
• Crystal phenomena
• Elasticity
• First-principles calculations
• Phase transitions
• Pressure effects
• Structural phase transition
• Structural properties
• Ab initio molecular dynamics