Some compounds of group III-V semiconductor materials exhibit very good piezoelectric,mechanical,and thermal properties and their use in surface acoustic wave(SAW) devices operating specially at GHz frequencies.These materials have been appreciated for a long time due to their high acoustic velocities,which are important parameters for active microelectromechanical systems(MEMS) devices.For this object,first-principles calculations of the anisotropy and the hydrostatic pressure effect on the mechanical,piezoelectric and some thermal properties of the(B3) boron phosphide are presented,using the density functional perturbation theory(DFPT).The independent elastic and compliance constants,the Reuss modulus,Voigt modulus,and the shear modulus,the Kleinman parameter,the Cauchy and Born coefficients,the elastic modulus,and the Poisson ratio for directions within the important crystallographic planes of this compound under pressure are obtained.The direct and converse piezoelectric coefficients,the longitudinal,transverse,and average sound velocity,the Debye temperature,and the Debye frequency of(B3) boron phosphide under pressure are also presented and compared with available experimental and theoretical data of the literature. Some compounds of group III-V semiconductor materials exhibit very good piezoelectric, mechanical, and thermal properties and their use in surface acoustic wave (SAW) devices operating at at GHz frequencies. These materials have been appreciated for a long time due to their high acoustic velocities, which are important parameters for active microelectromechanical systems (MEMS) devices. For this object, first-principles calculations of the anisotropy and the hydrostatic pressure effect on the mechanical, piezoelectric and some thermal properties of the (B3) boron phosphide are presented, using the density functional perturbation theory (DFPT). The independent elastic and compliance constants, the Reuss modulus, Voigt modulus, and the shear modulus, the Kleinman parameter, the Cauchy and Born coefficients, the elastic modulus, and the Poisson ratio for directions within the important crystallographic planes of this compound under pressure are obtained. The direct and converse piezoelectric coefficien ts, the longitudinal, transverse, and average sound velocity, the Debye temperature, and the Debye frequency of (B3) boron phosphide under pressure are also presented and compared with available experimental and theoretical data of the literature.