Structure studies of graded amorphous carbon obtained by liquid carbon quenching

A new method for obtaining graded amorphous carbon using quenching of a graphite melt on a diamond substrate is proposed. Using molecular dynamics modeling of liquid carbon quenching on a cold diamond substrate, it is shown that the amorphous carbon obtained in the experiment is a material with a strongly gradient structure and properties along the depth of the sample. This is due to the quenching rate decrease with the distance from the substrate in the range of 10$^{14}$–10$^{12}$ K/s. In this case, the density of amorphous carbon varies from 1.50 g/cm$^3$ to 1.93 g/cm$^3$. The spatial change in the structural characteristics of the obtained amorphous carbon was studied: the distribution of carbon atoms according to the degree of chemical bond hybridization ($sp^1$-, $sp^2$-, $sp^3$-), the radial distribution function, the angular distribution function, and a statistical analysis of carbon rings were carried out. It is shown that at a pressure in liquid of 1 GPa, the carbon structure within the quenched zone changes from a highly porous structure with a large number of $sp^1$ chains of carbon atoms near the substrate to an amorphous graphene structure at the periphery.