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1.
In this work, a new superhard material named Pm BN is proposed. The structural properties, stability, mechanical properties, mechanical anisotropy properties, and electronic properties of Pm BN are studied in this work. Pm BN is dynamically and mechanically stable, the relative enthalpy of Pm BN is greater than that of c-BN, and in this respect, and it is more favorable than that of T-B3N3, T-B7N7, tP24 BN, Imm2 BN, NiAs BN, and rocksalt BN. The Young's modulus, bulk modulus, and shear modulus of Pm BN are 327 GPa, 331 GPa, and 738 GPa, respectively, and according to Chen's model, Pm BN is a novel superhard material. Compared with its original structure, the mechanical anisotropy of Young's modulus of Pm BN is larger than that of C14 carbon. Finally, the calculations of the electronic energy band structure show that Pm BN is a semiconductor material with not only a wide band gap but also an indirect band gap. 相似文献
2.
本文采用基于密度泛函理论的第一性原理平面波赝势和局域密度近似方法,优化了立方和六方氮化硼的几何结构,系统地研究了零温高压下立方和六方氮化硼的几何结构、力学、电学以及光学性质.结构与力学性质研究表明:立方氮化硼的结构更加稳定,两种结构的氮化硼均表现出一定的脆性,而六方氮化硼的热稳定性则相对较差;电学性质研究表明:立方氮化硼和六方氮化硼均为间接带隙半导体,且立方氮化硼比六方氮化硼局域性更强;光学性质结果显示:立方氮化硼和六方氮化硼对入射光的通过性都很好,在高能区立方氮化硼对入射光的表现更加敏感.此外,还研究了高温高压下立方氮化硼的热力学性质,并得到其热膨胀系数、热容、德拜温度和格林艾森系数随温度和压力的变化关系.本文的理论研究阐述了高压下立方氮化硼和六方氮化硼的相关性质,为今后的实验研究提供了比较可靠的理论依据. 相似文献
3.
对立方氮化硼的空位进行了基于密度泛函理论框架下的第一性原理平面波超软赝势方法的研究. 通过对总能量、能带结构、态密度及电子密度分布图的分析发现, B空位相比起N空位更加稳定. 并且空位仅影响最近邻原子的电子分布, 空位浓度的增加使禁带宽度逐渐变窄. 从复介电函数和光学吸收谱分析中发现, 随着空位浓度的增加, 立方氮化硼在深紫外区的吸收逐渐减弱. 并且B空位还导致在可见光区域出现明显的吸收带.
关键词:
立方氮化硼
空位
第一性原理
电光学特性 相似文献
4.
Under high pressure conditions, we have obtained samples of samarium-activated cubic boron nitride in the form of micropowders,
ceramic samples, and polycrystals having high-intensity discrete photoluminescence in the red region of the spectrum that
is stable in the temperature range 6 K to 300 K and is assigned to internal f-f electronic transitions in the Sm3+ ions. The materials obtained on the basis of cBN are intended for use as phosphors and light emitters (sources of red light)
having thermal and chemical stability.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 88–93, January–February, 2008. 相似文献
5.
E. M. Shishonok L. Trinkler S. V. Leonchik B. Berzinya 《Journal of Applied Spectroscopy》2008,75(4):567-575
Under high pressure and temperature conditions, we have obtained samples of thulium-activated cubic boron nitride in the form
of micropowders, ceramics, and polycrystals activated by thulium in the presence of aluminum. We studied the cathodoluminescence
(CL), photoluminescence (PL), and photoluminescence excitation spectra of the samples. In the luminescence spectra we observe
structured bands with maxima at ∼370, ∼475, ∼660, and ∼ 800 nm, assigned to electronic transitions in the triply charged thulium
ions. We have established that the most efficient method for excitation of “blue” luminescence at ∼475 nm for thulium ions
in cBN is excitation by an electron beam. The cBN samples synthesized in the presence of Al have photoluminescence spectra
with a more complex structure compared with samples not containing Al, with the band of dominant intensity at about 660 nm.
Hypothetically, this is a consequence of incorporation of thulium ions into the crystalline phases cBN and AlN, which are
equally likely to be formed during synthesis. The observed photoluminescence spectrum of the indicated samples is the superposition
of the photoluminescence spectra of the Tm3+ ions located in the crystal fields of cBN and AlN of different symmetries. The presence in the photoluminescence excitation
spectra (at 450, 490, and 660 nm) of structure, with features at wavelengths shorter than the excited photoluminescence, suggests
a nonresonant mechanism for its excitation. We have established that luminescence of Tm3+ ions is less intense than for other rare earth elements incorporated into cubic boron nitride.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 547–555, July–August, 2008. 相似文献
6.
叶原丰 《原子与分子物理学报》2009,26(6)
本文采用密度泛函B3LYP方法在6-31G*水平上,对一系列不同宽度的锯齿型和扶手椅型六角氮化硼纳米带进行了理论研究。结果表明纳米带宽度对体系的性质有规律性的影响。随着宽度的增加,纳米带不同位置的硼氮键键长差异逐步减小从而提高了整个体系的共轭性;锯齿型纳米带的能隙单调减小而扶手椅型纳米带的能隙在减小的同时出现振荡,且振幅随宽度逐渐减小。锯齿型氮化硼纳米带的化学势在特定宽度出现了极值点。前线分子轨道的分布随着宽度的增加出现了非均匀分布,呈现出向边界偏移的现象。 相似文献
7.
本文采用密度泛函B3LYP方法在6-31G*水平上,对一系列不同宽度的锯齿型和扶手椅型六角氮化硼纳米带进行了理论研究。结果表明纳米带宽度对体系的性质有规律性的影响。随着宽度的增加,纳米带不同位置的硼氮键键长差异逐步减小从而提高了整个体系的共轭性;锯齿型纳米带的能隙单调减小而扶手椅型纳米带的能隙在减小的同时出现振荡,且振幅随宽度逐渐减小。锯齿型氮化硼纳米带的化学势在特定宽度出现了极值点。前线分子轨道的分布随着宽度的增加出现了非均匀分布,呈现出向边界偏移的现象。 相似文献
8.
Density functional theory calculations have been used to investigate the rolling process of armchair boron nitride nanoribbons (n-ABNNRs, n?=?6,?8,?10,?12,?14,?16) to form (n,?0) zigzag boron nitrogen nanotubes (ZBNNTs, n?=?3–8). Results showed that by rolling (increasing the curvature) energy gap decreases and the difference between the initial and final states increases dramatically with decreasing the ribbon width. It was found that ZBNNTs have direct band gaps and the gap increases by diameter, while ABNNRs have direct band gaps which oscillate with the ribbon width. 相似文献
9.
基于安德森紧束缚模型,本文研究了无序双层六角氮化硼量子薄膜的电子性质. 数值计算结果表明在双层都无序掺杂的情况下,六角氮化硼量子薄膜的电子是局域的, 其表现为绝缘体性质;而对于单层掺杂(无论是氮原子还是硼原子)的双层六角氮化硼量子薄膜, 在能谱的带尾出现了持续的迁移率边.这就说明在单层掺杂的双层六角氮化硼量子薄膜中产生了 金属绝缘体转变.这一结果证实了有序-无序分区掺杂的理论模型,为理解及调控双层六角氮化硼量子薄膜 的电子性质提供了有益的理论指导. 相似文献
10.
Based on a force constant model, we investigated the phonon spectrum and then specific heat of single-walled boron nitride nanotubes. The results show that the frequencies of Raman and infrared active modes decrease with increasing diameter in the low frequency, which is consistent with the results calculated by density functional theory. The fitting formulae for diameter and chirality dependence of specific heat at 300K are given. 相似文献
11.
Murat Durandurdu 《哲学杂志》2016,96(18):1950-1964
The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions. 相似文献
12.
Studying the surface properties of cubic boron nitride (c-BN) thin films is very important to making it clear that its formation mechanism and application. In this paper, c-BN thin films were deposited on Si substrates by radio frequency sputter. The influence of working gas pressure on the formation of cBN thin film was studied. The surface of c-BN films was analyzed by X-ray photoelectron spectroscopy (XPS), and the results showed that the surface of c-BN thin films contained C and O elements besides B and N. Value of N/B of c-BN thin films that contained cubic phase of boron nitride was very close to 1. The calculation based on XPS showed that the thickness of hexagonal boron nitride (h-BN) on the surface of c-BN films is approximately 0.8 nm. 相似文献
13.
Based on the first-principles method,we predict two new stable BN allotropes:C12-BN and O16-BN,which belong to cubic and orthorhombic crystal systems,respectively.It is confirmed that both the phases are thermally and dynamically stable.The results of molecular dynamics simulations suggest that both the BN phases are highly stable even at high temperatures of 1000 K.In the case of mechanical properties,C12-BN has a bulk modulus of 359 GPa and a hardness of 43.4 GPa,making it a novel superhard material with potential technological and industrial applications.Electronic band calculations reveal that both C12-BN and O16-BN are insulators with direct band gaps of 3.02 e V and 3.54 e V,respectively.The XRD spectra of C12-BN and O16-BN are also simulated to provide more information for possible experimental observation.Our findings enrich the BN allotrope family and are expected to stimulate further experimental interest. 相似文献
14.
15.
Abstract A simple method to determine the temperature of synthesis was proposed. (Mishima et al., to be published) This method utilized the melting of NaCl as an indicator of heater temperature. Applying the method to the fabrication of cBN p-n diodes in a large volume belt-type apparatus, we obtained an UV LED of ~2 mm in size. 相似文献
16.
17.
Optical properties of hexagonal boron nitride thin films deposited by radio frequency bias magnetron sputtering 下载免费PDF全文
The optical properties of hexagonal boron nitride (h-BN) thin films
were studied in this paper. The films were characterized by Fourier
transform infrared spectroscopy, UV--visible transmittance and
reflection spectra. h-BN thin films with a wide optical band gap Eg (5.86 eV for the as-deposited film and 5.97 eV for the
annealed film) approaching h-BN single crystal were successfully
prepared by radio frequency (RF) bias magnetron sputtering and
post-deposition annealing at 970~K. The optical absorption behaviour
of h-BN films accords with the typical optical absorption
characteristics of amorphous materials when fitting is made by the
Urbach tail model. The annealed film shows satisfactory structure
stability. However, high temperature still has a significant
effect on the optical absorption properties, refractive index n,
and optical conductivity σ of h-BN thin films. The
blue-shift of the optical absorption edge and the increase of Eg probably result from stress relaxation in the film under high temperatures. In addition, it is found that the refractive index
clearly exhibits different trends in the visible and ultraviolet regions.
Previous calculational results of optical conductivity of h-BN
films are confirmed in our experimental results. 相似文献
18.
Boron nitride nanotubes (BNNTs) are semiconductors with a wide band gap. In comparison with carbon nanotubes (CNTs), BNNTs have higher chemical stability, excellent mechanical properties and higher thermal conductivity. In this paper, we study the effect of diameters and substituting B and N atoms of various zigzag BNNTs with Al, on structural and electronic properties of BNNTs in solid state using the density functional theory method. The results of calculations of density of states and band structure (band) showed that the band gap between the valence and conduction level increases as a result of the enhancement of tube diameter of BNNTs. Finally, the results showed that the electronic properties of the pristine BNNTs can be improved by doping Al atom in the zigzag configuration of tubes. 相似文献
19.
Abstract The lattice parameters of turbostratic boron nitride (tBN) have been measured to 6.1 GPa at room temperature using energy-dispersive powder diffraction with synchrotron radiation. A fit to the experimental p-V data using Birch-Murnaghan equation of state gives values of the tBN bulk modulus 17.5(8) GPa and its pressure derivative ll.4(5). These values point to significantly higher compressibility of turbostratic BN as compared to three-dimensionally ordered graphite-like hexagonal and rhombohedral boron nitride. 相似文献