### MOLECULAR DYNAMICS SIMULATION OF THE DIFFUSION BEHAVIOUR IN Ti-Ag

Š. SVOBODA, M. LEBEDA, P. VLČÁK, J. DRAHOKOUPIL

Nanocon 2023

#### ABSTRACT

Ti-Ag alloy system is interesting for its biocompatibility and bioadhesion properties, therefore it is promising for the production of bone implants. Classical molecular dynamics was used to simulate diffusion in the Ti-Ag system. It is very suitable for this purpose. It provides the positions of the atoms at each time step, from which it is possible to obtain the mean square displacement, which can be used to easily calculate the diffusion coefficient. The disadvantage, however, is the huge computational complexity and so we have to limit ourselves to a

very small number of atoms (in this work only about 100,000) and very short time intervals (in this case only 6 ns)

### ATOMISTIC SIMULATIONS OF ION IMPLANTATION: THE SPUTTERING EFFECT ON DEPTH DISTRIBUTIONS

M. Lebeda, J. Drahokoupil, P. Vlčák

Nanocon 2023

#### ABSTRACT

Within the domain of molecular dynamics simulations investigating the ion implantation phenomena, the precise incorporation of the sputtering effect is important for accurate predictions of surface properties and the spatial distribution of implanted particles throughout the target material. However, this becomes computationally demanding task, especially for middle-to-high fluences, owing to the substantial number of atoms required for such simulations. In this study, a novel approach was introduced to address this issue. Sputtering effects based on yield data from the Monte Carlo TRIDYN software were integrated into the molecular dynamics simulations using an in-house algorithm implemented within the LAMMPS code. This integration significantly reduces the computational time, allowing for efficient simulations. The practicality of this algorithm is demonstrated by its application in predicting depth distributions of N particles implanted within an α-Ti target as a function of N fluence. The simulation results with and without the inclusion of the sputtering are compared, and validated with established TRIDYN simulations and experimental data obtained via GD-OES. This work showcases an efficient and pertinent approach for predicting high-dose ion implantation effects.

### MOLECULAR DYNAMICS SIMULATIONS OF NITROGEN ION CHANNELING IN α-TITANIUM TARGET

M. Lebeda, J. Drahokoupil, P. Vlčák

Nanocon 2022

#### ABSTRACT

Implanting N ions into Ti-based materials improves their

properties such as hardness, corrosion resistance, or friction

coefficient. During the implantation, significant number of ions can be guided through crystal channels, resulting into larger

penetration depths (i.e., ion channeling) and smaller number of

crystal defects. An important characteristic of ion-implanted

materials is ion distribution across the depth of the target.

Depending on the parameters of implantation, depth distributions can be strongly affected by the channeling effect. In this work, we used molecular dynamics (MD) simulations to predict the N ion channeling in hex. α-Ti at 0.5-4 keV kinetic energies, different surface orientations, target temperature, and incident angle.

### ATOMISTIC SIMULATION OF NITROGEN ION IMPLANTATION INTO α-TITANIUM TARGET

M. Lebeda, Z. Weiss, J. Lorinčík, I. Elantyev, P. Veřtát, J. Drahokoupil, P. Vlčák

Nanocon 2021

#### ABSTRACT

Implantation of nitrogen particles into titanium target changes (improves) its hardness and tribological properties in the depth ranging from a few up to hundreds of nanometers. In order to understand how these properties are influenced, it is important to determine the N concentration across the depth of the modified target. However, different experimental methods determining atomic distributions are subjected to various instrumental errors and samples imperfections. To obtain expected atomic distributions without such errors, computer simulations are being advantageously used. In this work, using atomistic molecular dynamics (MD) method and our self-implemented time saving algorithm for ion implantation, we predict N depth distributions and their characteristics in α-Ti as a function of N fluences. The MD data are compared with TRIM and with experimental profiles obtained by SIMS and GD-OES. We confirm that the MD distributions improve TRIM predictions, have in general good correspondence with the experiments, and suggest expected distributions for an ideal implantation situation.

### AB-INITIO STUDY OF SURFACE ENERGIES AND STRUCTURAL INFLUENCE OF VACANCIES IN TITANIUM NITRIDE NANOLAYER

M. Lebeda, P. Vlčák, J. Drahokoupil

Nanocon 2020

#### ABSTRACT

Titanium nitride (TiN) is largely applied as protective nanolayer of medical titanium implants due to its significant positive influence on the surface properties such as friction and corrosion resistance. During the process of its phase formation, occurrence of the point defects is probable and can potentially affect various material properties, e.g. change the lattice parameters. The surface energies of 8 crystallographic planes and effects of nitrogen vacancies on the lattice parameter in rock salt-like structure of TiN (δ-TiN) were studied using ab-initio method of density functional theory (DFT) with the generalized gradient approximation functional (GGA) as parametrized by Perdew, Burke and Ernzerhof (PBE). TiN supercell with 64 atomic positions was used for the calculation of defects influence and the results are thoroughly discussed in the context of available theoretical and experimental literature data. The linear decrease of lattice parameter with the increasing presence of nitrogen vacancies up to ca. 80 % was observed.The surface energy of (100) crystallographic plane is two times lower (1.499 J/m2) than for the rest of the studied planes.