The search for a band of a defect predicted above 4000 cm -1 in diamond through infrared vibrational spectra: a quantum mechanical investigation.

For many years, the atomic structures of several defects in diamond with high wavenumber (>4000 cm), including "amber centers", H1b, and H1c, have been investigated, but a conclusive explanation is still lacking. In this paper, we propose a novel model for the N-H bond under repulsion, with an expected vibrational frequency exceeding 4000 cm. Additionally, potential defects called NVH are proposed to investigate their correlation with these defects. Three NVH defects are considered, denoting a charge of = +1, = 0, and = -1 for NVH, NVH04, and NVH, respectively. Subsequently, the geometry, charge, energy, band structure, and spectroscopic characterization of the three defects NVH, NVH04, and NVH are analysed. Then, the calculated harmonic modes of NVH defects are used as a benchmark for studying NVH. The simulations indicate that, with the use of scaling factors, the highest NVH harmonic infrared peaks are 4072 cm, 4096 cm, and 4095 cm with PBE, PBE0, and B3LYP, respectively, along with a calculated anharmonic infrared peak at 4146 cm. These calculated characteristic peaks closely match those observed in "amber centers" (4065 cm and 4165 cm). However, based on the additional simulated anharmonic infrared peak at 3792 cm, NVH cannot be assigned to the 4165 cm band. It is possible to assign the 4065 cm band to NVH; even though it can remain stable in diamond at 1973 K, establishing and measuring this benchmark could be challenging. Although NVH is uncertain as a structure in "amber centers", a model of the N-H bond under repulsion stretching is proposed, which can generate a vibrational frequency surpassing 4000 cm. It may provide a useful avenue for investigating high wavenumber defect structures in diamond.