Diamond Crystal Lattice Research Articles

Автоматизированная идентификация природных ограненных алмазов (бриллиантов) по спектру люминесценции

The problem of recognition of natural and synthetic diamonds (diamonds) is relevant today. A technique for computer processing of the luminescence spectra of diamonds using the Origin mathematical package is proposed. The processing technique is presented on specific examples. The spectra were measured using a RAOS-3 spectrometer-fluorimeter. A laser with a wavelength of 532 nm was used to excite diamond luminescence. A method is proposed for identifying diamonds of unknown origin by the number of bands of elementary components in the luminescence spectrum when decomposed into Gaussian curves. Luminescence spectra in faceted diamonds (brilliants) are widely used to study their physical properties. Synthetic faceted diamonds are significantly inferior to natural ones in terms of luminescence intensity. The light signal of photoluminescence in the former, in some cases, is comparable with the noise level of the measuring device. As a result, the instantaneous value of the useful signal can take both positive and negative values over the entire wavelength range of the spectrum. Therefore, the detection of a useful signal against the background of interference is of great importance. Along with this, to identify a diamond, it is necessary to solve the problem of decomposing the spectrum into elementary components in the form of Gaussian curves. Since it has been established that the spectra of natural diamonds consist of two peaks, while synthetic diamonds contain from three to eight peaks, which indicates a loose structure of the diamond crystal lattice. The efficiency of solving a number of these problems can be significantly improved by using software applications with special functionality. To demonstrate the features and advantages of the automated technique, the Origin mathematical package was taken, which, in particular, makes it possible to improve the quality of the results of processing a low luminescence spectrum and to find the number of peaks for Gaussian curves with sufficient accuracy.

Comparison of bone ingrowth between two porous titanium alloy rods with biogenic lamellar structures and diamond crystal lattice on femoral condyles in rabbits

PurposeThe comparison of bone ingrowth between two types of porous titanium alloy rods with different micro-architectures including diamond crystal lattice (Re-rod) and biogenic lamellar configurations (Bi-rod) on femoral condyles was investigated in this study. MethodsTwelve rabbits were used. Re-rod (Re-rod group) and Bi-rod (Bi-rod group) were implanted randomly in femoral condyles of each rabbits respectively. Bone ingrowth of these two rods were investigated and compared. 4 and 12 weeks after the operation, X-ray, micro-CT and histological examinations were performed. ResultsNo femoral condyle fracture and rod defluxion in the two groups was noted in the X-ray images during the observation period. Micro-CT images showed that all metal trabeculae in the Bi-rod group were covered by new bone at 4 and 12 weeks, whereas partial metal trabeculae in the Re-rod group were still uncovered at 12 weeks. Histological images showed that there was new bone growth in the centre and periphery of Bi-rods at 4 and 12 weeks, and there were several areas without new bone ingrowth at 4 and 12 weeks in the centre of Re-rods. In micro-CT analysis, the bone volume to total volume (BV/TV) of the volume of interest (VOI) of the Bi-rod group was higher than in the Re-rod group [(0.0794 ± 0.0021) % Vs (0.0521 ± 0.0032) % and (0.0875 ± 0.0039) % Vs (0.0702 ± 0.0028) % respectively, P < 0.05] at 4 weeks and 12 weeks. Whereas, the mean trabecular thickness (Tb.Th) values of VOI between the two groups were not significantly statistically different at 4 and 12 weeks. In histological analysis, the BV/TV of the VOI of the Bi-rod group was higher than in the Re-rod group [(0.0624 ± 0.0021) % Vs (0.0435 ± 0.0028) % and (0.0675 ± 0.0024) % Vs (0.0476 ± 0.0031) % respectively, P < 0.05] at 4 weeks and 12 weeks. ConclusionThese results showed that Bi-rods got better bone ingrowth in femoral condyles of rabbits compared with Re-rods.

Tracking nitrogen-to-nickel ratio and prevalent paramagnetic species in synthetic diamonds by electron spin resonance at 90 K

Nitrogen and nickel are the main impurities in the type Ib synthetic diamonds obtained under high pressure and high temperature conditions using nickel-containing catalysts. Nitrogen enters the synthesized diamond from the air. The nickel/nitrogen ratio for the two types of diamonds, obtained with and without an aluminum getter that prevents the diamond crystal lattice from nitrogen penetration, was studied by electron spin resonance at 90 K.

Ultrasmall Nanodiamonds: Perspectives and Questions.

Nanodiamonds are at the heart of a plethora of emerging applications in areas ranging from nanocomposites and tribology to nanomedicine and quantum sensing. The development of alternative synthesis methods, a better understanding, and the availability of ultrasmall nanodiamonds of less than 3 nm size with a precisely engineered composition, including the particle surface and atomic defects in the diamond crystal lattice, would mark a leap forward for many existing and future applications. Yet today, we are unable to accurately control nanodiamond composition at the atomic scale, nor can we reliably create and isolate particles in this size range. In this perspective, we discuss recent advances, challenges, and opportunities in the synthesis, characterization, and application of ultrasmall nanodiamonds. We particularly focus on the advantages of bottom-up synthesis of these particles and critically assess the physicochemical properties of ultrasmall nanodiamonds, which significantly differ from those of larger particles and bulk diamond.

Computationally Designed Crystal Structures of the Supertetrahedral Ga4C and Ga4Si Solids.

The structural, mechanical, electrical, and optical properties of new supertetrahedral structures cF-Ga4X (X = C, Si) were studied by using a solid state DFT calculation. The crystal structures of cF-Ga4X are built based on a diamond crystal lattice, in which pairs of adjacent carbon atoms are replaced by Ga4X fragments, where Ga4 is a tetrahedron of gallium atoms. Calculations have shown that new mixed-type supertetrahedral structures are dynamically stable, have densities of 3.49 g/cm3 (X = C) and 2.65 g/cm3 (X = Si), and are narrow band gap semiconductors. From the performed molecular dynamics calculations, it follows that the homogeneous melting temperature of the gallium-carbon structure is in the range from 600 to 700 K and that of the gallium-silicon structure is in the range from 400 to 500 K.

Performance analysis of diamond-based masers

Masers, the microwave analog of lasers, are an important class of devices that can be used to generate highly coherent and stable microwave signals as well as quantum-limited amplification of microwave photons. Recently, the interest in such devices has increased, probably owing to experiments demonstrating the successful operation at room temperature of solid-state maser employing defects in diamond. These defects, called nitrogen vacancy (NV) centers, are comprised of a negatively charged substitutional nitrogen that replaces one of the diamond crystal lattice’s carbons and a vacancy adjacent to the excluded carbon atom. The performance of diamond-based masers, in terms of gain, noise, bandwidth, frequency of operation, and saturation, greatly depends upon the specific diamond crystal composition and its geometry in the respective microwave device. The currently available data on these issues are scarce and sometimes conflicting. It is, therefore, important to provide additional experimental data, complemented by theoretical analysis, to further optimize the required diamond material and thus enhance the capabilities of diamond-based maser technology. The latter is currently limited to operate only as an oscillator at very small bandwidths, with low saturation power. Here, we provide experimental results on a set of important parameters affecting diamond maser operation, such as the population and linewidth of the electron spin energy levels of the NVs under light illumination, as well as their relaxation times for several different diamond material compositions. These results are then used to point out which diamond material compositions and crystal geometry may be best suitable for maser-type applications.

Nanocrystals of face-centred cubic carbon, i-carbon and diamond obtained by direct conversion of graphite at high temperatures and static ultra-high pressures

Until recently graphite, diamond and amorphous carbon were considered to be the only three carbon modifications of a terrestrial origin present in nature. Recently numerous publications indicated the existence of two other uncommon metastable carbon allotropes - face-centred cubic carbon and i‑carbon – on Earth. Nanoparticles of these carbon allotropes were found in carbon spherules of samples taken from soils and rocks in different countries of Europe and North America, crude oil, ice sheets from Greenland, etc. The existence of these metastable carbon allotropes in nature appeared to confirm the Younger Dryas extraterrestrial impact hypothesis proposing such an impact over North America, that caused a global catastrophe and climate change. This hypothesis suggests an extraterrestrial impact origin of these carbon allotropes due to dynamic shock compression, since to date they have only been simultaneously produced in ultra-high pressures dynamic shock experiments. We report the first synthesis of nanocrystals of the both metastable carbon allotropes along with diamond at elevated temperatures and static ultra-high pressures. This provides evidence that nanocrystals of face-centred cubic carbon and i‑carbon present in nature are likely to form in Earth's mantle, so that they have a terrestrial origin. Results of electron diffraction and high-resolution transmission electron microscopy clearly indicate that face-centred cubic carbon and i‑carbon are characterized by unique crystal lattices, which have nothing common with the diamond crystal lattice. These two carbon allotropes are thought to be characterized by unconventional chemical bonds due to unusual combinations of their crystal lattice types and lattice parameters. The nature of chemical bonds in face-centred cubic carbon and i‑carbon is supposed to be different from that of conventional basic chemical bonds (covalent, ionic and metallic bonding as well as the van der Waals forces). These carbon allotropes can therefore possess unique and potentially valuable properties suitable for different applications.

Tight-binding calculations of the optical properties of Si nanocrystals in a SiO2 matrix.

We develop an empirical tight binding approach for the modeling of the electronic states and optical properties of Si nanocrystals embedded in a SiO2 matrix. To simulate the wide band gap SiO2 matrix we use the virtual crystal approximation. The tight-binding parameters of the material with the diamond crystal lattice are fitted to the band structure of β-cristobalite. This model of the SiO2 matrix allows us to reproduce the band structure of real Si nanocrystals embedded in a SiO2 matrix. In this model, we compute the absorption spectra of the system. The calculations are in an excellent agreement with experimental data. We find that an important part of the high-energy absorption is defined by the spatially indirect, but direct in k-space transitions between holes inside the nanocrystal and electrons in the matrix.

A 3D Printed Porous Titanium Alloy Rod with Diamond Crystal Lattice for Treatment of the Early-Stage Femoral Head Osteonecrosis in Sheep.

Instruments made of porous titanium alloy and fabricated with a 3D printed technique are increasingly used in experimental and clinical research. To date, however, few studies have assessed their use in early-stage osteonecrosis of the femoral head (ONFH). In this study, porous titanium alloy rods (Ti-Rod) with diamond crystal lattice, fabricated using an electron beam melting (EBM) technique, were implanted into sheep models (n=9) of early-stage ONFH for 6 months. Bone ingrowth and integration were investigated and compared with those of sheep (n=9) undergoing core decompression (CD) alone. Following Ti-Rod implantation, femoral heads showed fine osteointegration, with X-ray evaluation showing compact integration between peripheral bone and rods without radiolucent lines encircling the rods, as well as new bone growth along the metal trabeculae without the intervention of fibrous tissue. The regions of interest (ROIs) of femoral heads showed fine bone ingrowth after Ti-Rod implantation than CD alone. By micro-CT evaluation, the ratios of bone volume to total volume (BV/TV) of ROIs in Rod group was 930 % and 452 % higher than CD group after 3 (0.206 ± 0.0095 vs. 0.020 ± 0.0058, p < 0.05, n=3) and 6 (0.232 ± 0.0161 vs. 0.042 ± 0.0061, p < 0.05, n=3) months respectively. By histological evaluation, the BV/TV of ROIs in Rod group was 647 % and 422 % higher than CD group after 3 (0.157 ± 0.0061 vs. 0.021 ± 0.0061, p < 0.05, n=3) and 6 (0.235 ± 0.0145 vs. 0.045 ± 0.0059, p < 0.05, n=3) months respectively. The new bone grew along metal trabeculae into the center of the rod with a rapid bone ingrowth in Rod gorup. Whereas in CD group, new bone grew mainly at the periphery of the decompressive channel with a slow bone ingrowth. Mechanical analysis showed that maximum load on the femoral head-necks was 31 % greater 6 months after Ti-Rod implantation than after CD alone when the vertical press reached the apex (3751.75 ± 391.96 vs. 2858.25 ± 512.91 N, p < 0.05, n=3). The association of rod implantation with fine bone ingrowth, osteointegration, and favorable mechanical properties suggests that implantation of the porous titanium alloy rod with the diamond crystal lattice may be a beneficial intervention for patients with early-stage ONFH.

Сравнительный анализ спектров люминесценции алмазов

AbstractTo identify the signs that distinguish natural diamonds from artificial diamonds, a comparative analysis of the luminescence spectra with regards to the Q factor, center of gravity, bandwidth parameter, and energy losses in the diamond crystal lattice under conditions of ohmic and dielectric relaxation of luminescence is performed. The phenomenon of resonant luminescence in the femtosecond time range is detected in diamond. It is established that natural and artificial diamonds noticeably differ in the relaxation frequency and in the energy of resonant radiation.

Highly intensive emission of the NV− centers in synthetic HPHT microdiamonds at low nitrogen doping

Synthetic high-pressure high-temperature (HPHT) microdiamonds demonstrate strong resonant-like enhancement of the NV− photoluminescence (PL) at unexpectedly low concentration of the substitutional nitrogen atoms (NS) of 90 ppm, which is significantly smaller than the ∼250 ppm characteristic for conventional HPHT synthesis. The EPR, Raman, and luminescent spectroscopies, including time-resolved PL, provide evidence that this is due to competition between the increase in PL with increasing concentration of the NV− centers and nonradiative deactivation of these centers by defects induced by the NS in the diamond crystal lattice. It is suggested that the intensity of the NV− center emission can be optimized by the appropriate choice of nitrogen doping concentration which does not substantially disrupt the diamond crystal lattice.

Effect of a Nitrogen Impurity on the Fundamental Raman Band of Diamond Single Crystals

The effect of nitrogen defects in natural and synthetic diamond single crystals on the position and half-width of the fundamental Raman band was investigated. Samples containing the main types of nitrogen lattice defects at impurity contents of 1–1500 ppm were studied. The parameters of the Stokes and anti-Stokes components in Raman spectra of crystals situated in a cell with distilled water to minimize the influence of heating by the exciting laser radiation were analyzed to determine the effect of a nitrogen impurity in the diamond crystal lattice. It was shown that an increase of impurity atoms in the crystals in the studied concentration range resulted in broadening of the Raman band from 1.61 to 2.85 cm–1 and shifting of the maximum to lower frequency from 1332.65 to 1332.3 cm–1. The observed effect was directly proportional to the impurity concentration and depended on the form of the impurity incorporated into the diamond lattice. It was found that the changes in the position and half-width of the fundamental Raman band for diamond were consistent with the magnitude of crystal lattice distortions due to the presence of impurity defects and obeyed the Gruneisen law.

Enhancing the brightness of electrically driven single-photon sources using color centers in silicon carbide

Practical applications of quantum information technologies exploiting the quantum nature of light require efficient and bright true single-photon sources which operate under ambient conditions. Currently, point defects in the crystal lattice of diamond known as color centers have taken the lead in the race for the most promising quantum system for practical non-classical light sources. This work is focused on a different quantum optoelectronic material, namely a color center in silicon carbide, and reveals the physics behind the process of single-photon emission from color centers in SiC under electrical pumping. We show that color centers in silicon carbide can be far superior to any other quantum light emitter under electrical control at room temperature. Using a comprehensive theoretical approach and rigorous numerical simulations, we demonstrate that at room temperature, the photon emission rate from a p–i–n silicon carbide single-photon emitting diode can exceed 5 Gcounts/s, which is higher than what can be achieved with electrically driven color centers in diamond or epitaxial quantum dots. These findings lay the foundation for the development of practical photonic quantum devices which can be produced in a well-developed CMOS compatible process flow.

Dependence of Synthetic Diamond Wear Rate on Lattice Orientation at Traditional Mechanical Treatment

The results of comparative studies of the rate of mechanical polishing of the surface of synthetic diamond in various directions and different crystallographic surface orientations are presented. A free abrasive on a cast-iron disk is used for polishing. A method is proposed for numerical simulation of the polishing of an arbitrarily oriented diamond surface, based on an estimation of changes in the internal energy of the diamond crystal lattice under the action of the abrasive. The method enables determination of the direction of polishing, which ensures the maximum processing rate of a diamond surface of any crystallographic orientation. The validity of the proposed method is confirmed experimentally.

Incorporation of Large Impurity Atoms into the Diamond Crystal Lattice: EPR of Split-Vacancy Defects in Diamond

Diamond is a unique mineral widely used in diverse fields due to its remarkable properties. The development of synthesis technology made it possible to create diamond-based semiconductor devices. In addition, doped diamond can be used as single photon emitters in various luminescence applications. Different properties are the result of the presence of impurities or intrinsic defects in diamond. Thus, the investigation of the defect formation process is of particular interest. Although hydrogen, nitrogen, and boron have been known to form different point defects, the possibility for large impurity atoms to incorporate into the diamond crystal structure has been questioned for a long time. In the current paper, the paramagnetic nickel split-vacancy defect in diamond is described, and the further investigation of nickel-, cobalt-, titanium-, phosphorus-, silicon-, and germanium-related defects is discussed.

Studying the effect of hydrogen on diamond growth by adding C10H10Fe under high pressures and high temperatures

ABSTRACTIn this paper, hydrogen-doped industrial diamonds and gem diamonds were synthesized in the Fe–Ni–C system with C10H10Fe additive, high pressures and high temperatures range of 5.2–6.2 GPa and 1250–1460°C. Experimental results indicate similar effect of hydrogen on these two types of diamonds: with the increasing content of C10H10Fe added in diamond growth environment, temperature is a crucial factor that sensitively affects the hydrogen-doped diamond crystallization. The temperature region for high-quality diamond growth becomes higher and the morphology of diamond crystal changes from cube-octahedral to octahedral. The defects on the {100} surfaces of diamond are more than those on the {111} surfaces. Fourier transform infrared spectroscopy (FTIR) results indicate that the hydrogen atoms enter into the diamond crystal lattice from {100} faces more easily. Most interestingly, under low temperature, nitrogen atoms can also easily enter into the diamond crystal lattice from {100} faces cooperated with hydrogen atoms.

Syntheses of B2O3-doped gem-diamond single crystals

In the present paper, by the temperature gradient method, the gem-diamond single crystals with B2O3-added in the synthetic system of the FeNiMnCo-C are synthesized under 5.3-5.7 GPa and 1200-1600℃. The P-T phase diagram of diamond single crystal growing in the synthesis system of the FeNiMnCo-C-B2O3, is obtained. By B2O3-added in synthesis system, the V-shape section for the diamond growth, which is the region between the solvent/carbon eutectic melting line and diamond/graphite equilibrium line under pressure and temperature, is moved upwards. We find that the minimum pressure of diamond growing increases from 5.3 GPa to 5.4 GPa and the synthesis range of the low temperature hexahedron diamond growth becomes wider, which can be due to the chemical energy increase of the carbon depositing in the diamond surface by the additive of the B2O3. The synthetic diamond single crystal exhibits a perfect hexahedral shape or cubo-octahedral shape or octahedral shape. In the system of the FeNiMnCo-C-B2O3, we think that the catalyst activity decreases with the generation of CO2, so high-quality diamond single crystal can hardly be synthesized when the content of the B2O3 is more than 3 wt‰ and synthesis time is more than 20 h, However, when the content of the B2O3 is no more than 1 wt‰, the rate of finished products of the low temperature hexahedron diamond will increase significantly. Because the amount of the B2O3 additive is so small, in the syntheses of B2O3-added diamond single crystals, the black areas which appear when B element enters into diamond crystal lattice are not observed. The growth rate of diamond single crystal will be reduced obviously by B2O3-added in synthetic system. Under our system synthesis, when the growth time is 10 h, the growth rate of the diamond will reduce 0.22 mg/h by 2 wt‰ B2O3 added in synthetic system. When the growth time extends to 20 h, the growth rate increases to 0.47 mg/h. Moreover, with the extension of growth time, the catalyst activity decreases continuously with the product of the CO2 increasing in the reaction chamber, so the effect of additive on the growth of diamond strengthens gradually. The results of the scanning electron microscope images indicate that the surface defects of the diamond crystal increases by the addition of B2O3.

Supermolecular design: From molecules to solid states

A short review of the recent studies aimed at the search for novel stable polyhedral structures engineered by superstruction of the classical parent highly strained but kinetically stable organic predecessors, tetrahedrane, cubane, and dodecahedrane is presented. A series of stable structures B80H20, C80H20, and Al80H20 with tetrahedral B4H, C4H, and Al4H fragments displacing CH vertices of the cubane and dodecahedron scaffolds was computationally designed. In the similar way, the molecules С104H32, В104H32, В64С40H32 and В40С64H32, Al104H32, Si104H32 and Al64Si40H32 representing the supermolecular models of the corresponding crystal structures were constructed on the basis of the diamond crystal lattice in which carbon atoms are replaced by B4, C4, and Al4 and Si4 tetrahedral moieties, respectively. The effect of crystalline packing exerted on the conformation of the non‐rigid molecular structures is discussed by an example of supermolecular modeling of the structural configuration of a ten molecule sampling of a bis‐chelate Ni(II) complex. © 2015 Wiley Periodicals, Inc.

Interface thermal resistance between liquid water and various metallic surfaces

Enhancing thermal transport mechanisms in nanostructures and nanomaterials are important factors for their use in green renewable energy applications. The behaviors and reliability of nanoscale devices strongly depend on the way the systems dissipate heat. Therefore, using non-equilibrium molecular dynamics (MD) simulations, we investigated the interface thermal resistance between liquid water and various metallic surfaces in nanochannels. Solid-liquid interface thermal resistance is well known as the Kapitza length. In this study, we model heat transfer through two parallel solid walls separated by liquid water, holding each solid wall at a different temperature to impose a temperature gradient. Silicon with a diamond crystal lattice structure and copper, silver, gold, and platinum with face-centered cubic (FCC) crystal lattice structure were chosen as the solid materials due to their extensive applications in nanotechnology. Temperature jumps at such solid-liquid interfaces are due to thermal transport between the dissimilar materials, resulting in an interface thermal resistance. We observed the behaviors of liquid water molecules in the vicinity of the metallic surfaces, revealing that the Kapitza length varies as a function of solid-liquid interaction strength, and confirming the effect of Lennard-Jones (LJ) interaction added to long-range Coulombic interaction in the liquid model, and using liquid water instead of simple LJ liquid.

Crystal growth and characterization of hydrogen-doped single diamond with Fe(C5H5)2 additive

In this paper, a series of high-quality hydrogen-doped diamonds is successfully synthesized in Ni70Mn25Co5-C system by using Fe(C5H5)2 as hydrogen source at pressures ranging from 5.5 GPa to 6.0 GPa and temperatures of 1280-1400 ℃. We find that both pressure and temperature conditions strengthen with adding the Fe(C5H5)2. Scanning electron microscope micrographs show that the obtained diamonds at low levels of Fe(C5H5)2 additive have smooth surfaces. However, many defects are found and some pores appear on the diamond surface with increasing the Fe(C5H5)2 additive in the system. From the obtained Fourier transform infrared (IR) spectrum, we notice that there is no significant change of nitrogen concentration in the synthesized diamond with the Fe(C5H5)2 additive lower than 0.3 wt%, while the nitrogen concentration gradually decreases with the further increase of Fe(C5H5)2 additive. In the system with 0.5 wt% Fe(C5H5)2 additive, the nitrogen concentration in synthesized diamond is only half that of system without Fe(C5H5)2 additive. Meanwhile, the hydrogen associated IR peaks of 2850 cm-1 and 2920 cm-1 are gradually enhanced with the increase of Fe(C5H5)2 additive in the system, indicating that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp3-CH2-symmetric (2850 cm-1) and sp3 CH2-antisymmetric (2920 cm-1) vibrations. From the obtained Raman spectrum, we find the incorporation of hydrogen impurity leads to a significant shift of the Raman peak towards higher frequencies from 1333.90 cm-1 to 1334.42 cm-1 with increasing the concentration of Fe(C5H5)2 additive from 0.1 wt% to 0.5 wt%, thereby giving rise to some compressive stress in the diamond crystal lattice. This is the first time that the gem-grade hydrogen-doped diamond single crystal, with size up to 3.5 mm has been successfully synthesized by using new hydrogen source Fe(C5H5)2 additive. We believe that our work can provide a new method to study the influence of hydrogen impurity on diamond synthesis and it will help us to further understand the genesis of natural diamond in the future.