The origin of color in natural C center bearing diamonds

Substitutional nitrogen in diamond: A quantum mechanical investigation of the electronic and spectroscopic properties

“…These are in satisfactory agreement with the reported experimental spectrum of type Ib synthetic diamond. 27,32,33,[36][37][38] Conversely, there are no significant features in the Raman spectrum other than the strong 1317 cm −1 absorption of the perfect crystal. This is within 1.1% of the measured value 31 of 1332 cm −1 , which verifies the accuracy of the present frequency simulations.…”

“…This work, based on all electron, Gaussian type orbitals, B3LYP calculations and periodic supercells has provided an accurate description of the lattice and band structures, charge and unpaired spin density distributions and vibrational frequencies of the nitrogen substitution defect, N s , in diamond by comparison with available photoconduction and optical absorption 51,52,93 , IR 27,32,33,[36][37][38] and Raman 31 , and EPR 42 and ENDOR 41,43 data.…”

“…The spectrum appears quite similar to those obtained through the deconvolution procedure by Clark and Davey 34 and Woods 35 . The main features of the infrared absorption are: (i) a sharp local-mode absorption peak close to 1344 cm −1 ; (ii) a flattish hump between 1332 and 1200 cm −1 ; (iii) a broad band peaking at 1130 cm −1 with a shoulder at 1092 cm −1 ; (iv) a less intense signal at 1050 cm −1 ; and (v) a broad weak hump centered at 832 cm −1 , see also Refs 34,38,98,99. To facilitate a comparison with experiment, a full simulated spectrum was obtained by enveloping each S 216 frequency with a peudo-Voight function with a full width at half maximum of 30 cm −1 . A comparison of experimental 97 and simulated spectra is also shown in the same Figure 5, where a satisfactory match between the two is clearly evident, notably with regard to the distinctive features of the C-centre, which are correctly predicted, together with the low intense signals at 1050 and 832 cm −1 .…”

“…28,29 On the other hand, synthetic diamonds produced by CVD (carbon vapour deposition) and controlled HTHP (high temperature high pressure) grow generally as type Ib, but often, with minor amounts of other defects. 30 The single substitutional defect, N S , leads to a distinctive IR spectrum with characteristic vibrational modes [31][32][33][34][35][36][37][38] at 1130 and 1344 cm −1 ; it also gives rise to the P1 electron paramagnetic resonance (EPR) signal, which is how it was first discovered in 1959. 39 Both the early EPR and subsequent ENDOR studies [39][40][41][42][43] have shown that the P1 centre has an effective spin of S = 1 2 , a C 3v symmetry with the nitrogen atom, N S , displaced away from one of its four neighbours, and that most of the unpaired spin is located on just one of the carbon atoms neighbouring N S .…”

Fourier transform infrared spectroscopy data and carbon isotope characteristics of the ophiolite-hosted diamonds from the Luobusa ophiolite, Tibet, and Ray-Iz ophiolite, Polar Urals

“…Natural diamonds commonly contain nitrogen in abundance varying from a few to several thousand atomic ppm N and show large variations in aggregation states (Boyd et al, 1994). Kimberlitic diamonds type Ib are very rare (<0.1%; reviewed in Cartigny et al, 2004;Nadolinny et al, 2006;Hainschwang et al, 2013;Cartigny, 2010;Smit et al, 2016;Smith et al, 2016) and exhibit high nitrogen aggregation states and would plot on the right side of Figure 7 (IaAB diamonds, e.g., Javoy et al, 1984;Deines et al, 1997;Cartigny et al, 1997). This is because, in kimberlites and lamproites, most diamonds (>95%) are xenocrysts, which must have formed earlier when their host rocks equilibrated in the Earth's mantle (Richardson et al, 1984;Shirey et al, 2013, for review).…”