First-principles calculations of electronic, acoustic and anharmonic properties of Mn2RuZ (Z = Si and Ge) Heusler compounds

Highlights: • Determining the third-order elastic constants of Mn₂RuZ (Z = Si, Ge) for the first time. • Studying the acoustic and related properties of Mn₂RuZ (Z = Si, Ge) in terms of the elastic properties. • Studying the anharmonic properties of Mn₂RuZ (Z = Si, Ge) in terms of the elastic properties. The electronic, acoustic and anharmonic properties of Mn₂RuZ (Z = Si and Ge) Heusler compounds were systematically studied by first-principles calculations combined with homogeneous deformation theory. The calculated lattice constants, electronic, magnetic and elastic properties were found to agree with the available experimental and theoretical values. Based on the obtained elastic properties, the acoustic velocities, Debye temperatures and thermal conductivities were calculated for both compounds. Their acoustic velocities and thermal conductivities were found to exhibit anisotropic behavior. Mn₂RuSi has larger acoustic velocities, higher Debye and thermal conductivities for its lower density and larger second-order elastic constants. The pressure derivatives of second-order elastic constants, mode Grüneisen constants of long-wavelength acoustic modes, and nonlinear ultrasonic parameters were also obtained. The predictions on the acoustic and anharmonic properties are useful for further study of the related materials in the near future.