X-ray diffraction experiments have been carried out on InP at room temperature to pressures of 19 GPa. The compression curve for the zinc-blende phase (I) was found to fit the Murnaghan equation up to 10.8 GPa where a transformation to the rocksalt structure was observed. Values for the bulk modulus, $B_{\mathrm{I}0\mathrm{}}$ and its pressure derivative, $B_{\mathrm{I}0\mathrm{}{}^{\mathcal{’}}}$, at P=0 obtained by a best-fit procedure to the Murnaghan equation were $B_{\mathrm{I}0\mathrm{}=76\mathrm{}\pm 4}$ GPa and $B_{\mathrm{I}0\mathrm{}{}^{\mathcal{’}}=4\mathrm{}\pm 0.2}$. These values are similar to those obtained from precision elastic constant measurements. Analogous parameters for the rocksalt phase (II) were obtained with reference to the transition pressure $B_{\mathrm{II}\mathit{t}=130\mathrm{}\pm 10}$ GPa, $B_{\mathrm{II}\mathit{t}=1.6\mathrm{}\pm 0.1}$. At 19 GPa a further transformation was observed to a phase which was tentatively identified as β-Sn-like. Data for these three phases are given and discussed in terms of models for the transitions.

• Received 13 January 1987

DOI:https://doi.org/10.1103/PhysRevB.35.7520