Molecular dynamics simulation of bituminous coal and anthracite conversion to diamond
ZHANG Zhijun
LI Zhenqing
TANG Di
SHANG Xiulin
Abstract：To elucidate the microscopic mechanisms underlying the conversion of coal to dia-mond and promote the clean and efficient utilization of coal resources,the processes of heteroa-tom removal,diamond nucleation,and diamond growth in coal were simulated using reactive force field molecular dynamics(ReaxFF MD).The results indicate a positive correlation be-tween pyrolysis temperature and the yield of both inorganic and organic gases.After three cy-cles of heteroatom removal at 4 000 K,the carbon content reached 98.54％for bituminous coal and 98.83％for anthracite.During the diamond nucleation stage,the minimum pressure(pmin)required for coal diamond nucleation negatively correlates with temperature and posi-tively correlates with the rate of pressure increase.The pmin of bituminous coal is higher than that of anthracite,and both coal types form hexagonal diamond nuclei.In the diamond growth stage,the diamond conversion rate increases with pressure.Elevated reaction temperature and reduced pressure increase rates significantly enhance the diamond conversion rate.At 4 000 K,with pressure elevated to 80.00 GPa at a rate of 0.05 GPa/ps,the diamond conversion rates reached 46.97％for bituminous coal and 45.77％for anthracite.Increasing the pressure to 80.00 GPa at 0.1 GPa/ps(4 000 K)and extending the time under constant temperature and pressure significantly improved the diamond conversion rate of bituminous coal.After 350 ps at constant temperature and pressure,the conversion rate increased from 29.68％to 53.65％for bituminous coal and from 21.32％to 31.27％for anthracite.Following diamond nuclea-tion,a transitional growth phase occurred,during which the conversion rates for both coal types gradually increased with pressure.During the high-temperature and high-pressure con-version process,mutual transformations between diamond and non-diamond structures oc-curred,as well as between cubic and hexagonal diamond structures.
Keywords：coaldiamondhigh-temperature and high-pressurereactive force fieldmolecular dynamics simulation
Publication Date：2025-09-30
Online Publishing Date：2025-10-31(First online date of this platform, not the publication date of the document)
Pages：15( 1137-1151 )