  Available information concerning the elastic moduli of refractory carbides at
temperatures (T) of relevance for practical applications is sparse and/or
inconsistent. We carry out ab initio molecular dynamics (AIMD) simulations at T
= 300, 600, 900, and 1200 K to determine the temperature-dependences of the
elastic constants of rocksalt-structure (B1) TiC, ZrC, HfC, VC, and TaC
compounds as well as multicomponent high-entropy carbides (Ti,Zr,Hf,Ta,W)C and
(V,Nb,Ta,Mo,W)C. The second order elastic constants are calculated by
least-square fitting of the analytical expressions of stress vs. strain
relationships to simulation results obtained from three tensile and three shear
deformation modes. Moreover, we employ sound velocity measurements to evaluate
the bulk, shear, elastic moduli and Poisson's ratios of single-phase B1
(Ti,Zr,Hf,Ta,W)C and (V,Nb,Ta,Mo,W)C at ambient conditions. Our experimental
results are in excellent agreement with the values obtained by AIMD
simulations. In comparison with the predictions of previous ab initio
calculations - where the extrapolation of finite-temperature elastic properties
accounted for thermal expansion while neglecting intrinsic vibrational effects
- AIMD simulations produce a softening of elastic moduli with T in closer
agreement with experiments. Results of our simulations show that TaC is the
system which exhibits the highest elastic resistances to both tensile and shear
deformation up to 1200 K, and identify the high-entropy (V,Nb,Ta,Mo,W)C system
as candidate for applications that require good ductility and toughness at room
as well as elevated temperatures.
