Quantifying the anomalous self-diffusion in molybdenum with first-principles simulations

Abstract

First-principles molecular-dynamics simulations based on a recently developed exchange-correlation functional show that self-diffusion in the refractory metal molybdenum is associated with strongly temperaturedependent activation energies for vacancy formation and migration. While static calculations of self-diffusion rates based on transition-state theory deviate systematically from experiments, with up to two orders of magnitude, the current results are accurate to within a mean deviation of 4 over the experimental range in temperature.

Simulation Of Ion Implantation Into Nuclear Materials And Comparison With Experiment

“…Specifically, 500 keV Xe ions were implanted into a single-crystal CeO 2 TEM specimen at 600 °C to an accumulated dose of 2x10 16 ions/cm 2 . Figure 5 shows the atomic-level crystal structures of the specimen before and after irradiation.…”

First-principles design of next-generation nuclear fuels

“…Temperature-dependent DFT has been successfully applied to describe materials behavior over a wide range in temperature, up to almost 1000ºC. 11 , 12 , 14 , 15 , 19 Using temperaturedependent DFT in combination with MD simulations, Mattsson et al 42 computed the anomalous temperature evolution of the vacancy formation energy in Mo up to about 2700ºC, and Root et al 43 studied xenon's behavior at extreme conditions of high pressure and high temperature. Although T -dependent (temperature dependent) DFT can thus be employed to hightemperature dynamic and thermodynamic properties, it has not yet been applied to nuclear materials.…”

“…Furthermore, the defect jump rate and absolute concentration can be calculated as a function of temperature using the DFT-based MD. 42 MD is implemented in several DFT simulation packages. 45 , 46 Current limitations on supercell size are a third area deserving of research attention.…”

Thermoelectric transport properties of molybdenum fromabinitiosimulations

“…For Mo, the AM05 exchange-correlation functional 50,51 gives very good equilibrium density and bulk modulus 5 and was therefore used in all calculations above 4 g/cm 3 . For expanded states, we used the PBE functional 52 instead since PBE gives good atomization energies, a property that is important in the region around the critical point.…”

“…Three examples of effects due to the involved electronic structure are the positive signs of the thermopower 3 and Hall coefficient 4 near ambient conditions and the anomalous self-diffusion behavior at high temperature below the melting point. 5 The electrical conductivity, σ, in solid molybdenum is accurately known up to the melting point 6 at ambient pressure. It was also measured in the liquid phase [7][8][9][10] and in plasma states 11 using exploding wire experiments.…”