Modified unit cell of Fe3AlC (K-phase) that can act as a substrate for a diamond growth was proposed. Spin-polarized calculations were performed to compare electronic structure of carbon atoms in K-phase substrate, diamond and graphite. Standard enthalpies of formation of different K-phase unit cells were calculated and compared with formation enthalpy of modified unit cell of K-phase.

Calculations of electron structure of supercells consisting of several layers of ordinary stoichiometric K-phase and modified K-phase, on which according to our assumptions epitaxial growth of diamonds is possible, were conducted. Stability of calculated cells was considered, and optimal number of layers of the stoichiometric K-phase in the supercell was determined in order for it to be thermodynamically stable. Electronic structure of carbon in the modified K-phase layer was considered and compared to electron structure of carbon in diamond.

Calculations of electron structure of supercells consisting of several layers of ordinary stoichiometric K-phase and modified K-phase, on which according to our assumptions epitaxial growth of diamonds is possible, were conducted. Stability of calculated cells was considered, and optimal number of layers of the stoichiometric K-phase in the supercell was determined in order for it to be thermodynamically stable. Electronic structure of carbon in the modified K-phase layer was considered and compared to electron structure of carbon in diamond.

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 Fe3C 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 Fe3AlC, Fe3.125Al0.825C0.5, Fe3.5Al0.5C0.5, Fe3.5Al0.5C, Fe3Al0.66C0.66, and Fe3AlC0.66 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 Fe3AlC0.66 (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.