Effects of the surface structure and cluster bombardment on the self-sputtering of molybdenum

Abstract

The understanding of different features of the sputtering of materials lies in understanding the factors contributing to the emission of atoms from a regular crystal structure at the surface. Although the sputtering of fcc crystals has received much attention, the database on bcc materials is still scarce. We use molecular dynamics simulations to study the self-sputtering of the (100), (110), (111) and (112) surfaces of molybdenum. Single atoms as well as Mo 2 and Mo 4 clusters are used as the irradiation projectiles, in the cluster energy range of 0.125-4 keV. Contrary to the usual assumption, enhanced (nonlinear) sputtering yields are observed for the cluster bombardments at both ends of the energy range studied. The enhancements can be explained with lower threshold energies for sputtering at low energies and with a decreased fraction of channelled projectile atoms in the kiloelectronvolt energy range.

Spatial distribution of particles sputtered from single crystals by gas cluster ions

“…The simulations were performed with the PARCAS code [6][7][8]. The Lennard-Jones potential was used for the Ar-Ar interactions, the EAM potentials [9][10] for the Mo-Mo and Cu-Cu interactions and the density-functional theory based pair-specific repulsive potentials [11] for the Ar-Mo and Ar-Cu interactions. The size of the simulation cell was 50x50x40 unit cells for Cu target and 48x48x48 unit cells for Mo target with periodic boundary conditions in x and y directions.…”

Computational study of crystal defect formation in Mo by a machine learning molecular dynamics potential

“…Transition metals and alloys are traditionally modeled by the embedded atom method (EAM) potentials in MD simulations [5,[8][9][10], reproducing many material properties in good agreement with those measured experimentally. However, EAM and other traditional potentials are limited to fixed functional forms [1,8] and can wrongly model some point defects that are energetically unstable, or lack physical meaning in material damaging processes [11].…”

Optimization of single crystal mirrors for ITER diagnostics

“…The exposure continued for 40 minutes, the samples were biased to -65 V as the actual mirrors. The resulting ion fluence was 3.7×10 20 ion/cm 2 . The temperature during the exposure was in the range of 240 o C -255 o C. After exposure, mass loss measurements were performed.…”

“…The ions were hitting a square box with the side length of 4 lattice constants, at 27 o C (300 K), similarly to previous studies on tungsten [18]. The interactions between Mo atoms were described by the Ackland et al potential [19], with the addition of Ziegler-Biersack-Littmark potential by Salonen et al [20]. Between the Ar and Mo atoms the potential from the DMol package [21] was used.…”