Lowest energy structures of self-interstitial atom clusters in -iron from a combination of Langevin molecular dynamics and the basin-hopping technique

ランジュバン分子動力学法とbasin-hopping法による鉄中の格子間原子型クラスターの最安定構造

阿部 陽介; 實川 資朗

Abe, Yosuke; Jitsukawa, Shiro

Langevin分子動力学法とbasin-hopping with occasional jumping(BHOJ)法を結びつけることにより、アルファ鉄中での格子間原子型(SIA)クラスターの最安定配位のサイズ依存性を系統的に求めた。最安定配位探索の高効率化のため、あるSIAクラスターにおいて相対的に結合の弱い原子をランダムに抽出し、他のSIAに隣接するサイトに移動させるlong jumpingプロセスを新たに導入した。求めた最安定配位における結合エネルギーを算出し、KMC法や反応速度論において直接使用可能な解析表現を得た。

A combination of simulated annealing with Langevin molecular dynamics and basin-hopping with occasional jumping (BHOJ) technique was used to systematically determine the most stable configurations of self-interstitial atom (SIA) clusters ( 1-38) in -iron. In addition to the original BHOJ technique, we introduced an additional long jumping process in which a randomly selected less-bounded atom is moved to a neighboring site of another SIA in the cluster to enhance the probability of locating the global minimum structure. With the obtained putative lowest energy structures, the binding energies as a function of cluster size were estimated. We also determined the sizes of particular stable clusters based on their geometrical symmetry. Furthermore, the values were extrapolated based on accurately determined formation energies, and are available for immediate use in kinetic Monte Carlo or rate theory models.