• Kindlund, Hanna
• Sangiovanni, D. G.
• Hultman, L.
• Lu, J.
• Chirita, V.
• Petrov, I.
• Greene, J. E.
• Jensen, J.

Abstract

<jats:p>The authors report the growth and mechanical properties of epitaxial B1 NaCl-structure V1−xWxN/MgO(001) thin films with 0 ≤ x ≤ 0.60. The Gibbs free energy of mixing, calculated using density functional theory (DFT), reveals that cubic V1−xWxN solid solutions with 0 ≤ x ≲ 0.7 are stable against spinodal decomposition and separation into the equilibrium cubic-VN and hexagonal-WN binary phases. The authors show experimentally that alloying VN with WN leads to a monotonic increase in relaxed lattice parameters, enhanced nanoindentation hardnesses, and reduced elastic moduli. Calculated V1−xWxN lattice parameters and elastic moduli (obtained from calculated C11, C12, and C44 elastic constants) are in good agreement with experimental results. The observed increase in alloy hardness, with a corresponding decrease in the elastic modulus at higher x values, combined with DFT-calculated decreases in shear to bulk moduli ratios, and increased Cauchy pressures (C12–C44) with increasing x reveal a trend toward increased toughness.</jats:p>

Topics

• density
• phase
• theory
• thin film
• spinodal decomposition
• hardness
• nanoindentation
• density functional theory