Substantiation of Epitaxial Growth of Diamond Crystals on the Surface of Carbide Fe3AlC0.66 Phase Nanoparticles

摘要

Samples of Fe–Al–C alloys of varying composition were synthesized under high pressures and temperatures. From X-ray analysis data, only K-phase with usual for it average parameter of elemental lattice cell, a ?=?0.376?nm, carbide Fe~(3)C and cubic diamond reflexes were present before and after cooling to the temperature of liquid nitrogen. Calculations were made of the parameters of unit cells, the enthalpy of formation of the Fe~(3)AlC, Fe~(3.125)Al~(0.825)C~(0.5), Fe~(3.5)Al~(0.5)C~(0.5), Fe~(3.5)Al~(0.5)C, Fe~(3)Al~(0.66)C~(0.66), and Fe~(3)AlC~(0.66) unit cells and crystallographic planes were identified on which epitaxial growth of the diamond phase was possible, using density functional theory as implemented in the WIEN2k package. The possibility of epitaxial growth of diamond crystals on Fe~(3)AlC~(0.66) (K-phase) nanoparticles was, therefore, demonstrated. The [200] plane was established to be the most suitable plane for diamond growth, having four carbon atoms arranged in a square and a central vacancy which can be occupied by carbon during thermal-and-pressure treatment. Distances between carbon atoms in the [200] plane differ by only 5% from distances between the carbon atoms of a diamond. The electronic structure and energetic parameters of the substrate were also investigated. It was shown that the substrate with at least four intermediate layers of K-phase exhibits signs of stability such as negative enthalpy of formation and the Fermi level falling to minimum densities of states.