Search

The electronic structure of an edge dislocation doped Ti lying in the (001) plane with Burgers Vector along [100] direction in body-centered cubic iron is investigated using the first principles discrete variational method (DVM) based on the density-functional theory. The binding energy, impurity formation energy, interatomic energy, Mulliken orbital populations and charge density difference are presented in this paper. By calculating the binding energy of the clean dislocation system and the Ti-doped system, it is found that the binding energy of Ti-doped dislocation system is lower than that of the clean dislocation system, which implies that the Ti-doped dislocation system is more stable than the clean dislocation system. The calculated result of the impurity formation energy predicts the trapping effect of dislocation core for Ti, which shows that Ti atom prefers to occupy the place at the dislocation core. The calculated results of the inter- atomic energy and the difference charge density of dislocation doped Ti system indicate that the stronger bonding formed between the Ti impurity and its neighbor Fe atoms will affect the mechanical property of edge dislocation. Considering the influence of Ti on the electronic structure and the energies, we can predict that the trace Ti in transition metal Fe with dislocation defect can give a significant contribution to the solid solution hardening effects and will influence the mechanical property of materials. [ABSTRACT FROM AUTHOR]

We perform a first-principles calculation to investigate the effect of a vacancy on the sliding of an iron (Fe) Σ5 (310) [001] tilt grain boundary (GB). We calculate vacancy formation energies in order to determine the site preference of the vacancy at the Fe GB. We show that vacancies can easily segregate to the GB region, which is attributed to special atomic configurations of the GB. We demonstrate that the maximal sliding energy barrier of the GB with a monovacancy is 2.78 J/m2, 15% lower than that of the vacancy-free GB, suggesting that the presence of vacancy at the GB increases the GB mobility. [ABSTRACT FROM AUTHOR]

The energetics and kinetics regarding helium (He) cluster growth in bcc tungsten (W) are unveiled using combined techniques of molecular statics and molecular dynamics. The principal mechanisms accounting for the decrease of system potential energy are identified to be trap mutation,   →   cluster transformation, loop punching, coalescence between 1/2[1 1-1] and 1/2[1-1-1] loops, and loop capturing. The kinetic barriers associated with these key atomistic events are estimated. This work provides new insights into the complex yet intriguing atomistic evolution sequence of the He cluster and interstitial loop in W-based nuclear fusion materials under irradiation. [ABSTRACT FROM AUTHOR]

We report a hydrogen induced vacancy formation mechanism in tungsten based on classical molecular dynamics simulations. We demonstrate the vacancy formation in tungsten due to the presence of hydrogen associated directly with a stable hexagonal self-interstitial cluster as well as a linear crowdion. The stability of different self-interstitial structures has been further studied and it is particularly shown that hydrogen plays a crucial role in determining the configuration of SIAs, in which the hexagonal cluster structure is preferred. Energetic analysis has been carried out to prove that the formation of SIA clusters facilitates the formation of vacancies. Such a mechanism contributes to the understanding of the early stage of the hydrogen blistering in tungsten under a fusion reactor environment. [ABSTRACT FROM AUTHOR]