Density functional study of elastic and vibrational properties of the Heusler-type alloys Fe2VAl and Fe2VGa

• The structural and elastic properties as well as phonon-dispersion relations of the Heusler-type alloys Fe2VAl and Fe2VGa are computed using density functional and density-functional perturbation theory within the generalized-gradient approximation. The calculated equilibrium lattice constants agree well with the experimental values. The elastic constants of Fe2VAl and Fe2VGa are predicted. From the elastic constants the shear modulus, Young's modulus, Poisson's ratio, sound velocities, and Debye temperatures are obtained. By analyzing the ratio between the bulk and shear moduli, we conclude that both Fe2VAl and Fe2VGa are brittle in nature. The computed phonon-dispersion relation shows that both compounds are dynamically stable in the L2(1) structure without any imaginary phonon frequencies. The isomer shifts in Fe in the two compounds are discussed in terms of the Fe s partial density of states, which reveal larger ionicity/less hybridization in Fe2VGa than in Fe2VAl. For the same reason the Cauchy pressure is negative in Fe2VAl but positive in Fe2VGa.

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NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

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Physics

Fysik

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