本文選題：硬度　切入點(diǎn)：B-C-N化合物　出處：《西南大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：超硬材料已經(jīng)廣泛應(yīng)用于制造磨料,涂料,切割,拋光工具等�，F(xiàn)代科學(xué)技術(shù)的迅速發(fā)展,對材料提出了越來越苛刻的性能要求。超硬材料的合成及其性質(zhì)研究,一直是凝聚態(tài)物理和材料科學(xué)研究的重點(diǎn)之一。除了金剛石與立方氮化硼(c-BN)以外,BC3、BC5、C3N4、RuO2、OsB2、立方氮碳化硼等材料也日益受到國際材料界的重視。在這些材料的研究中,理論計(jì)算已經(jīng)成為評估或預(yù)測材料硬度的有效工具。本論文應(yīng)用VASP(Vienna Ab-inito Simulation Package)和Materials Studio量化軟件包,以密度泛函為主要研究方法對由輕元素B、C、N、O等組成新型材料的彈性性質(zhì)、硬度、電子性質(zhì)進(jìn)行了系統(tǒng)的研究。主要研究內(nèi)容和結(jié)論如下:(1)材料的硬度大于40GPa的材料稱之為超硬材料。金剛石是已知的世界上最硬的超硬材料。金剛石具有極高的硬度,但是金剛石容易被氧化,并易于與鐵族金屬反應(yīng),因而限制了它的更廣泛的應(yīng)用。立方氮化硼(c-BN)具有高熱、化學(xué)穩(wěn)定性。然而,c-BN的硬度僅在46-66GPa的范圍內(nèi),這顯然遠(yuǎn)小于金剛石的硬度。鑒于此,本文基于金剛石的結(jié)構(gòu),構(gòu)建了1×1×3的超胞,按B、C、N原子比1:4:1取代金剛石超胞結(jié)構(gòu),構(gòu)建了C_8B_2N_2晶體結(jié)構(gòu),經(jīng)篩選而獲得較穩(wěn)定的t-C_8B_2N_2,運(yùn)用密度泛函理論下的局域密度近似和廣義梯度近似理論對t-C_8B_2N_2晶體結(jié)構(gòu)進(jìn)行了系統(tǒng)的研究。彈性常數(shù)和聲子計(jì)算,結(jié)果表明:t-C_8B_2N_2晶體結(jié)構(gòu)是熱力學(xué)和動力學(xué)穩(wěn)定的。除此之外,我們使用顯微結(jié)構(gòu)模型對極性共價(jià)的t-C_8B_2N_2晶體結(jié)構(gòu)的硬度進(jìn)行了研究。結(jié)果表明,t-C_8B_2N_2晶體結(jié)構(gòu)是潛在的新型超硬材料。(2)本文基于立方C6晶體結(jié)構(gòu),按B、C、N原子比1:1:1取代立方C6晶體結(jié)構(gòu),構(gòu)建得到6種穩(wěn)定的C_2B_2N_2晶體結(jié)構(gòu),經(jīng)篩選而獲得了較高體彈模量和剪切模量的P3m1-C_2B_2N_2晶體結(jié)構(gòu)。運(yùn)用密度泛函理論下的局域密度近似(LDA)和廣義梯度近似理論(GGA)對P3m1-C_2B_2N_2晶體結(jié)構(gòu)的彈性常數(shù)、聲子、電子結(jié)構(gòu)、硬度進(jìn)行了系統(tǒng)的研究。經(jīng)根據(jù)Born-Huang的力學(xué)穩(wěn)定性判據(jù)和聲子頻率計(jì)算,結(jié)果表明:P3m1-C_2B_2N_2晶體結(jié)構(gòu)是熱力學(xué)和動力學(xué)穩(wěn)定的。除此之外,我們使用顯微結(jié)構(gòu)模型對極性共價(jià)的P3m1-C_2B_2N_2晶體結(jié)構(gòu)的硬度進(jìn)行了研究,計(jì)算結(jié)果表明,P3m1-C_2B_2N_2晶體結(jié)構(gòu)的硬度(計(jì)算硬度67.5GPa)與立方氮化硼的硬度(計(jì)算硬度65.4GPa)相媲美。(3)重過渡金屬可在化合物中引入高價(jià)電子密度以抵抗彈性和塑性變形,因而重過渡金屬和輕元素形成的材料家族被認(rèn)為是潛在的超硬材料。實(shí)際上,高硬度的過渡金屬氮化物、碳化物和硼化物已經(jīng)被合成和報(bào)道。本文選取了具有較高體彈模量和剪切模量的Os、Pt、Re、Ru、Ir晶體結(jié)構(gòu),在螢石結(jié)構(gòu)構(gòu)建了Os、Pt、Re、Ru、Ir等元素的氮化物和氧化物。我們使用第一原理計(jì)算螢石(CaF2)結(jié)構(gòu)中Os、Pt、Re、Ru、Ir等元素的碳化物,氮化物和氧化物的體積彈性、剪切模量、楊氏模量、泊松比等彈性性質(zhì)。篩選得到具有較高體彈模量和剪切模量的ReO2、RuO2晶體結(jié)構(gòu)。經(jīng)根據(jù)Born-Huang的力學(xué)穩(wěn)定性判據(jù)和聲子頻率計(jì)算,結(jié)果表明:ReO2、RuO2晶體結(jié)構(gòu)是熱力學(xué)和動力學(xué)穩(wěn)定的。同時(shí)ReO2、RuO2晶體結(jié)構(gòu)的彈性性質(zhì)計(jì)算也證明:ReO2、RuO2是潛在的不可壓縮的超硬材料。
[Abstract]:Super hard materials have been widely used in the manufacture of abrasive, coating, cutting, polishing tools. The rapid development of modern science and technology, put forward more and more demanding performance of materials. The synthesis and properties of super hard materials, has been one of the focuses of condensed matter physics and material science research. In addition to diamond and cubic boron nitride (c-BN), BC3, BC5, C3N4, RuO2, OsB2, cubic nitrogen boron carbide materials has attracted international attention. The research materials in these materials, the theoretical calculation has become an effective tool to evaluate or predict the hardness of the material. In this paper, the application of VASP (Vienna Ab-inito Simulation Package and Materials Studio) quantitative software package based on density functional as the main research method of the light element B, C, N, O etc. the new elastic properties, the hardness of materials, electronic properties were studied systematically. The main research contents and conclusions Are as follows: (1) hardness greater than 40GPa material called super hard material. The diamond is known to the world's most hard superhard material. Diamond has high hardness, but the diamond is easily oxidized, and is easy to react with iron group metals, which limits its wider application. Cubic boron nitride boron (c-BN) with high thermal, chemical stability. However, the hardness of c-BN only in the range of 46-66GPa, which is obviously far less than the hardness of diamond. In view of this, this paper based on the diamond structure, construction of 1 * 1 * 3 supercell, according to B, C, N atomic ratio of 1:4:1 to replace the diamond cell structure the crystal structure of C_8B_2N_2, construction, through screening and obtain stable t-C_8B_2N_2, by using the local density functional theory approximation and the generalized gradient approximation theory for the research on the crystal structure of t-C_8B_2N_2. The elastic constants and phonon calculations, the results showed that: t-C_8B The crystal structure of _2N_2 is thermodynamically and kinetically stable. In addition, we use the model of the microstructure of t-C_8B_2N_2 crystal structure of polar covalent hardness were studied. The results showed that the crystal structure of t-C_8B_2N_2 is a potential new superhard materials. (2) the cubic crystal structure of C6, based on B, C, N the atomic ratio of 1:1:1 to replace the C6 cubic crystal structure, construct 6 kinds of C_2B_2N_2 stable crystal structure, through screening and obtained the P3m1-C_2B_2N_2 crystal structure of high bulk modulus and shear modulus. By using the local density functional theory approximation (LDA) and the generalized gradient approximation (GGA) theory of elastic constants of P3m1-C_2B_2N_2 crystal structure the phonon, electron structure, hardness was studied. Through calculation, according to the Born-Huang stability criteria and the results show that the phonon frequency of P3m1-C_2B_2N_2 crystal structure and thermodynamic power Study of stability. In addition, we use the model of the microstructure of P3m1-C_2B_2N_2 crystal structure of polar covalent hardness were studied. The calculation results show that the crystal structure of P3m1-C_2B_2N_2 hardness (calculated hardness 67.5GPa) and cubic boron nitride hardness (calculated hardness 65.4GPa) comparable. (3) transition metal can be introduced at high prices the electron density in the compounds to resist the elastic and plastic deformation, so heavy and light transition metal elements form the material family is considered to be the potential superhard materials. In fact, the high hardness of transition metal nitrides, carbides and borides have been synthesized and reported. This paper has high bulk modulus and shear modulus Os Pt, Re, Ru, Ir, crystal structure, the fluorite structure constructed by Os, Pt, Re, Ru, Ir and other elements of the nitride and oxide. We use the first principle calculation of fluorite structure (CaF2) in Os, Pt, Re, Ru, Ir Other elements of the young's modulus of volume elasticity, carbide, nitride and oxide, shear modulus, Poisson's ratio and elastic properties were obtained. With high bulk modulus and shear modulus ReO2, the crystal structure of RuO2. By calculation, according to the Born-Huang stability criteria and the phonon frequency results show that: ReO2, RuO2 and crystal structure of thermodynamics dynamic stability. At the same time ReO2, the elastic properties of the crystal structure of RuO2 ReO2 RuO2, it is proved that calculation is the potential for incompressible super hard materials.

【學(xué)位授予單位】：西南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ163

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