In this contribution, we report extensive ab-initio calculations of elastic properties of Ti(Si)N(C) and Cr(Si)N(C) materials. Atom cores and inner electron shells are described by Vanderbilt-type pseudopotentials, and Kohn-Sham equations for valence electrons are expanded using a wave-basis set. In fcc metal nitride networks, up to 1/8 of metal atoms are replaced by Si, and up to 1/4 of N atoms by C.

For various material compositions, bulk modulus (B) and lattice constant (a₀) is calculated by fitting the Birch equation on total energies calculated at different lattice parameters (94-106 % of the lowest energy value), and elastic tensor (C_ij) is derived using energy changes resulting from small volume-preserving strains and shears (up to 6% and 6 deg., respectively). Young's modulus (E), Poisson's ratio (ν) and shear modulus (G) are calculated from C_ij. We examine dependence of density of unpaired spins on material composition and on the strains applied. We find that small Si or C contents in materials lead to decreasing G, increasing E₁₀₀, decreasing ν and slightly increasing a₀, and calculate slopes of the changes. Furthermore, B decreases after addition of Si while there are no changes in B after addition of C. Dependence of electrical conductivity on material composition is examined by calculating electronic density of states.

The results, compared with experimental data and explained using the changes in valence electrons wavefunction, can be used to estimate properties of the previously deposited and simulated nanocomposite structures. The calculated lattice constants can be used to estimate compositions of crystals examined by x-ray diffraction.

Titanium dioxide (TiO₂) films have been prepared using physical vapor deposition (PVD) processes for several decades. It is often considered as a material for applications such as photocatalysis, self-cleaning and antimicrobial purposes. However, numerous questions regarding the growth behavior and microstructure remain unanswered. This study aims to clarify, using microstructural characterization techniques and optical emission spectroscopy (OES), the conditions under which rutile or anatase phase constituents appear in films deposited by PVD arc ion plating (AIP), to give a better understanding of TiO₂ films deposited using different deposition processes.

The experimental results show that the calculated free energy for rutile phase growth is lower than for anatase, and that the rutile phase grows preferentially if thermodynamically satisfactory oxygen supply (in terms of oxygen partial pressure) is present, although less activation energy is required for anatase growth. However, OES studies reveal that, with further increased oxygen partial pressure and extended deposition time, oxidation occurring at the cathode surface generates a higher amount of neutral titanium atoms and, consequently, the metastable anatase phase grows. Detailed TEM microstructural characterization of the deposited TiO₂ films in this study also explicitly shows that films identified as XRD amorphous actually contain very fine rutile nanocrystallites within the amorphous structure, whereas films revealed by XRD as composed predominantly of the anatase phase are actually as a consequence of later growth, preceded by rutile growth in the initial stage.

Hard coatings are widely used in surface engineering for wear protection and friction reduction of mechanical components. Numerous different coatings are currently available for specific applications. Among these coatings, vanadium carbide (VC) thin films show high hardness, high melting point, and good chemical stability. However, the crystalline structure of VC thin films is still open to investigation. On one hand, stoichiometric VC is an interstitial compound, where vanadium forms the principal lattice and carbon occupies the octahedral interstitial sites¹. On the other hand, the equilibrium phase diagram of the V-C system is complex and many phases with different stoichiometries coexist².Although order-disorder phase transformations were already observed, the migration of carbon atoms associated with these transformations is still unclear³. In this work, vanadium carbide thin films were deposited on Si substrates by reactive magnetron sputtering f rom a V target in a Ar/CH₄ plasma, varying the Ar/CH₄ partial pressure ratio and substrate temperature. The films were characterized by glancing angle X-ray diffraction and Rutherford backscattering spectrometry. Better defined crystalline structures were obtained at higher CH₄ content than 13%. The increase of substrate temperature diminishes slightly the film thickness and substantially the C/V atomic ratio. The intensity ratio of the Bragg peaks (111)/(200) decreases as a function of substrate temperature. The results are discussed in terms of a proposed mechanism for interstitial diffusion of carbon atoms in vanadium carbide thin films with fcc-like crystalline structure and the carbon occupancy of tetrahedral or octahedral interstitial sites as a function of substrate temperature.

¹V. N. Lipatnikov, A. I. Gusev, P. Ettmayer, and W. Lengauer, J. Phys.: Condens. Matter 11, (1999) 163.

²J. Hu, C. Li, F. Wang, and W. Zhang, J. Alloys Compounds 421, 120 (2006).

³V.N. Lipatnikov, W. Lengauer, P. Ettmayer, E. Keil, G. Groboth, and E. Kny, J. Alloy and Comp. 261, 192 (1997).