Pressure Dependence of Structural and Mechanical Properties of Single-Crystal Tungsten: A Molecular Dynamics Study

Abstract

In the current study, molecular dynamics (MD) simulations were performed to study the pressure dependence of the structural and mechanical properties of single-crystal tungsten. The results show that single-crystal tungsten possesses noteworthy high-pressure stability and exhibits linear lattice contraction with increasing external pressure. Consistent with the results of the performed experiments, the predicted elastic moduli, including Young’s modulus, shear modulus, and bulk modulus, as well as Poisson’s ratio and Pugh’s modulus ratio, show a clear increasing trend with the increase in pressure. Under uniaxial tensile loading, the single-crystal tungsten at high pressures experiences a phase transition from BCC to FCC and other disordered structures, which results in a stripe-like morphology in the tungsten crystal. These results are expected to deepen our understanding of the high-pressure structural and mechanical behaviors of tungsten materials.

Molecular-Dynamics Analysis of the Mechanical Behavior of Plasma-Facing Tungsten

“…MD-computed representative stress–strain curves, at a strain rate of 10 8 s –1 , over the porosity range ϕ up to ∼8% for defective tungsten with empty voids and He bubbles are shown in Figures a and b, respectively. In both cases, the stress–strain curve for perfect tungsten (i.e., ϕ = 0%) is given by the black solid line that exhibits a significant stress drop (i.e., stress relief in the material) upon yielding (i.e., reaching the yield point where the stress exhibits a local maximum), which also has been reported in other studies . It can be seen from Figure that the stress–strain curves for PFC tungsten (with both empty voids and He bubbles) follow a qualitatively similar behavior with that of perfect tungsten with substantial stress relief following the yield point.…”

“…In both cases, the stress− strain curve for perfect tungsten (i.e., ϕ = 0%) is given by the black solid line that exhibits a significant stress drop (i.e., stress relief in the material) upon yielding (i.e., reaching the yield point where the stress exhibits a local maximum), which also has been reported in other studies. 56 It can be seen from Figure 4 that the stress−strain curves for PFC tungsten (with both empty voids and He bubbles) follow a qualitatively similar behavior with that of perfect tungsten with substantial stress relief following the yield point. From Figure 4, it is evident that in defective tungsten (ϕ > 0) the yield strength (equal to the peak stress or yield stress) decreases monotonically with increasing porosity whereas the corresponding yield strain increases monotonically in both cases.…”