A modified W-W interatomic potential based on ab initio calculations

Based on ab initio calculations, a Finnis-Sinclair-type interatomic potential for W-W interactions has been developed. The modified potential is able to reproduce the correct formation energies of self-interstitial atom defects in tungsten, offering a significant improvement over the Ackland-Thetford tungsten potential. Using the modified potential, the thermal expansion is calculated in a temperature range from 0 K to 3500 K, and the results are in reasonable agreement with the experimental data, thus overcoming the shortcoming of the negative thermal expansion using the Derlet-Nguyen-Manh-Dudarev tungsten potential. The present W-W potential is also applied to study in detail the diffusion of self-interstitial atoms in tungsten. It is revealed that the initial self-interstitial atom initiates a sequence of W atom displacements and replacements in the <111> direction. An Arrhenius fit to the diffusion data at temperatures below 550 K indicates a migration energy of 0.022 eV, in reasonable agreement with the experimental data.