The first-formed hydrogen and nitrogen defects in natural diamond

Nitrogen (N) and hydrogen (H) defects in diamond provide crucial information about diamond growth. The electromagnetic properties that N/H-defects impart on synthetic diamond are exploited in novel technological applications including quantum information storage and sensing. Access to the Gemological Institute of America database of infrared spectra recorded from rare Type Ib + IaA natural diamonds has allowed identification of the first-formed N/H-defects, NH 0 and N 2 H 0 , assigned to IR peaks at 3394 and 3343 cm −1 , respectively. Density functional perturbation theory and ab initio molecular dynamic simulations of NH 0 and N 2 H 0 , including the first machine-learning molecular dynamics simulation performed for N/H-defects in diamond, show excellent agreement between observed and calculated C H stretching frequencies (18 to 66 cm −1 difference). New aggregation sequences are proposed for V N 3 H 0 , the commonly observed end-state of N/H-aggregation, that differ from the currently accepted sequence. This suggests that NH 0 and N 2 H 0 form during, or shortly after, diamond formation inhibiting diffusive loss of H during mantle residence and thus the H (isotopic) composition of diamond may reflect parental fluids from primordial and/or recycled mantle H 2 O reservoirs. These findings also have important technological implications for N/V-defects, such as NV − , with useful electromagnetic properties that may be passivated by H.