Using first-principles quantum molecular dynamics (QMD) calculations, heterostructures consisting of one monolayer of interfacial SixNy inserted between several monolayers of thick slabs of B1(NaCl)-TiN (001) and (111) were investigated in the temperature range of 0 to 1400 K. For the interpretation of the interfacial structures, samples of amorphous SiN and Si3N4 were also generated. The temperature-dependent QMD calculations in combination with subsequent variable-cell structural relaxation revealed that the TiN(001)/B1-SiN/TiN(001) interface exists as a pseudomorphic B1-SiN layer only at 0 K. At finite temperature, this heterostructure transforms into distorted octahedral SiN6 and tetrahedral SiN4 units aligned along the {110} directions. At 300 K, the aggregates of the SiNx units are close to a disordered, essentially amorphous SiN. After heating to 1400 K and subsequent relaxation at 300 K, the interfacial layer corresponds to a strongly distorted Si3N4-like structure. The B1-SiN, Si3N4-like SiN, and Si3N4-like Si2N3 interfaces between the TiN(111) slabs are stable in the whole temperature range considered here. The B1-SiN interfaces are unstable with respect to a formation of Si-vacancies at finite temperatures. An estimate of interfacial formation energies showed that the most favorable configurations of the (111) interfaces are silicon atoms tetrahedrally coordinated to nitrogen. The most stable (001) B1-derived heterostructure with Si0.75N interface consists of both tetrahedrally and octahedrally coordinated silicon atoms. A comparison with the results obtained by earlier ``static'' ab initio calculations at 0 K shows the great advantage of the QMD calculations, which accounts for the effects of thermal activation of structural reconstructions.

Heterostructures with one monolayer of interfacial SiC inserted between several B1(NaCl)-TiN (001) and (111) slabs are investigated in the temperature range of 0\char21{}1400 K using first-principles quantum molecular dynamics (QMD) calculations. The temperature-dependent QMD calculations in combination with subsequent variable-cell structural relaxation reveal that the TiN(001)/B1-SiC/TiN(001) interface exists as a pseudomorphic B1-SiC layer at temperatures between 0 and 600 K. After heating to 900\char21{}1400 K and subsequent static relaxation, the interfacial layer corresponds to a strongly distorted 3C-SiC-like structure oriented in the (111) direction in which the Si and C atoms are located in the same interfacial plane. The Si atoms form fourfold coordinated Si-C3N1 configurations, whereas the C atoms are located in C-Si3Ti2 units. All (111) interfaces calculated at 0, 300, and 1400 K have the same atomic configurations. For these interfaces, the Si and C layers correspond to the Si-C network in the (111) direction of 3C-SiC. The Si and C atoms are located in Si-C3N1 and C-Si3Ti3 configurations, respectively. The ideal tensile strength of all the heterostructures is lower than that of TiN. A comparison with the results obtained from earlier ``static'' ab initio density functional theory calculations at 0~K for similar heterostructures shows the great advantage of QMD calculations that reveal the effects of thermal activation on structural reconstructions.

Due to the increased demands for drilling and cutting tools working at extreme machining conditions, protective coatings are extensively utilized to prolong the tool life and eliminate the need for lubricants. The present work reports on the effect of a second MeN (Me = Zr, Cr, Mo, Nb) layer in WN-based nanocomposite multilayers on microstructure, phase composition, and mechanical and tribological properties. The WN/MoN multilayers have not been studied yet, and cathodic-arc physical vapor deposition (CA-PVD) has been used to fabricate studied coating systems for the first time. Moreover, first-principles calculations were performed to gain more insight into the properties of deposited multilayers. Two types of coating microstructure with different kinds of lattices were observed: (i) face-centered cubic (fcc) on fcc-W₂N (WN/CrN and WN/ZrN) and (ii) a combination of hexagonal and fcc on fcc-W₂N (WN/MoN and WN/NbN). Among the four studied systems, the WN/NbN had superior properties: the lowest specific wear rate (1.7 × 10⁻⁶ mm³/Nm) and high hardness (36 GPa) and plasticity index H/E (0.93). Low surface roughness, high elastic strain to failure, Nb₂O₅ and WO₃ tribofilms forming during sliding, ductile behavior of NbN, and nanocomposite structure contributed to high tribological performance. The results indicated the suitability of WN/NbN as a protective coating operating in challenging conditions.

Structures and mechanical properties of thin films of the Nb–Al–N system produced by magnetron sputtering of targets from niobium and aluminum in the Ar–N2atmosphere have been studied. It has been...