Experimental Justification of the Influence of S and Ni on Crystallization of Low-Nitrogen Diamonds in a Melt of Fe at High Pressure

Based on analysis of the results of the synthesis and growth of diamonds in metal-sulfide melts at a high pressure, the cause of the crystallization of low-nitrogen diamond crystals is substantiated. The introduction of sulfur into an iron melt leads to a decrease in the solubility of nitrogen, which, in turn, leads to a decrease in the content of nitrogen atoms in the melt and the probability of their capture by growing diamond crystals in the form of a structural impurity. The addition of nickel reduces the melting point of the growth system, increases the amount of melt, and, accordingly, facilitates the dissociation of molecular nitrogen into separate atoms, which are captured as a structural impurity by diamonds during their growth.