新型二维材料的热动力学稳定性及其电子结构的调控
发布时间：2019-05-22 10:06
【摘要】：二维纳米材料因维度受限而具有很多新奇的性质,已经成为材料科学研究的前沿领域。最近,石墨炔(graphdiyne)和以单层黑磷(black-phosphorene)为代表的二维V族纳米材料因所具有的优异性质引起了人们的巨大关注,随着研究的不断深入,逐渐展现出巨大的应用潜力。为了拓宽以上两类材料的应用领域,且便于以它们为基的纳米器件设计,从理论角度深入研究石墨炔和二维V族纳米材料的物理性质显得十分必要。基于此,我们做了下述工作:1.采用分子动力学方法,并基于自适应的分子反应键序势---AIREBO势,我们系统地研究了单层石墨炔(graphyne和graphdiyne)在高温下的演化行为。结果表明,在熔化过程中,单层石墨炔(graphyne和graphdiyne)将经历三个连续的相变。首先,单层的graphyne和graphdiyne分别从2800和2500 K时开始转变成初始的无定形graphene相(AGP),简称为初相;接着,该初相会通过一结构调整过程逐渐演化成无定形graphene相,这个过程一直会持续直至温度升高到3650 K。该无定形graphene相会保持相对稳定直到温度进一步上升到大约5000 K;最后,当温度进一步上升高于5000 K后,该无定形gaphene相会逐渐转变成近似液态。单层graphyne和graphdiyne在高温下的剧烈收缩和随后的伸展在形成初始的无定形graphene相的过程中起了决定性的作用。不同于著名的KTHNY理论关于二维材料熔化的预测,在单层的graphyne和graphdiyne升温的过程中,我们并没有观察到标志性的中间相---Hexatic相,而是无定形graphene相(AGP)。2.基于第一性原理计算,我们研究了以氢原子和羟基官能团(-OH)化学修饰graphyne和graphdiyne对它们结构稳定性的影响以及对它们电子结构的调控效应。(1)发现零点能在评估氢化graphyne的稳定性时起重要作用。基于计算的形成焓,我们发现仅存有sp2杂化的碳原子的graphyne氢化构型(命名为eHH)比每个碳原子上只吸附一个氢原子的graphyne氢化构型(命名为eH)更加稳定。但是亥姆霍兹自由能与温度的关系曲线表明,当温度低于670 K时,eH比eHH更加稳定。通过计算声子谱,我们确定eH和eHH是动力学稳定的氢化graphyne构型。令人感兴趣的是,graphyne的带隙特征会随着graphyne上氢原子覆盖率的增加而经历一个直接到间接再到直接的转变。(2)研究了羟基(-OH)修饰graphyne和graphdiyne的低能量构型及其电子结构。在高密度羟基修饰的低能量构型中,由于羟基官能团间氢键的稳定化作用,在相邻的大三角碳环和六角碳环上羟基官能团会形成手性状结构。与氢化的graphyne和graphdiyne构型相比,当羟基官能团把graphyne和graphdiyne中的碳碳键全部饱和成单键后的构型是不稳定的。结果还表明,羟基官能团在系统中可以导致磁性,但是这种磁性性质只能存在于低羟基覆盖率的构型中。两个羟基官能团间形成氢键的羟基对使系统一般不显示磁性,这是因为两个羟基在系统中导致的磁矩是反铁磁耦合的。3.基于第一性原理计算预测了两种新型孔状二维碳同素异形体,命名为Cy和Cz。二者具有比graphdiyne更低的形成能。分子动力学模拟表明,即使温度高于大约1000 K,Cy和Cz依旧可以保持其热力学稳定性。它们的泊松比显示它们具有各向异性的力学性质。电子结构计算表明,Cy是一种金属而Cz显示为一种半导体。而且Cz具有各向异性的导电性,这表明了Cz在纳米电子器件领域的应用潜力。它们还具有特定尺寸且规律性分布的孔状结构,有潜力成为新型的分子筛。4.基于第一性原理计算提出了三种具有奇异结构和性质的二维单层磷氮(PN)材料,分别命名为α-PN、β-PN和γ-PN。α-PN和γ-PN都具有弯曲的构型,而β-PN则显示出折叠的特征。它们的新奇构型使这些单原子层的PN材料具有很高的热动力学稳定性及很强的各向异性的力学性质。它们都是间接带隙的半导体,而且它们的能隙对面内的单轴应变具有高度的敏感性。这三种单层的PN材料被裁剪成纳米带后呈现出显著的量子尺寸效应。尤其是,α-PN的锯齿形纳米带显示出依赖尺寸的铁磁性。这些重要的性质表明了它们在纳米电子器件领域中应用的潜力。我们还从理论上提出了实验合成这三种PN单层相的可能途径,这值得在实验中进一步研究。5.基于声子谱计算和有限温度下的第一性原理分子动力学模拟,我们发现了一种新型的tricyle形的二维砷烯(arsenene),简称为T-As。T-As的结构坚固且在较高温度下仍可以保持热力学稳定。T-As的能量稳定性可与先前报道的chair形arsenene(C-As)相比拟,且比stirrup形arsenene(S-As)更加稳定。不同于C-As和S-As,单层的T-As是一种直接带隙的半导体,其能隙为1.377 eV。我们的结果表明,通过堆垛、应变、裁剪的方式都可以有效的调控T-As的电子性质,表明其在未来的纳米电子器件领域具有应用的潜力。而且,通过在T-As表面沿一个特定方向吸附氢或氟原子,可获得具有特定边缘类型以及宽度的纳米带,这有利于其被制成纳米器件。
[Abstract]:The two-dimensional nano-material has many novel properties due to the limitation of the dimension, and has become the frontier field of material science research. Recently, the excellent properties of the two-dimensional V-group nano-material represented by the graphdiyne and the single-layer black-phosphorus are of great concern to the people, and with the development of the research, the great application potential is gradually displayed. In order to broaden the application field of the two kinds of materials, and to facilitate the design of the nano-devices based on them, it is necessary to study the physical properties of the graphene and the two-dimensional V-group nano-materials from a theoretical point of view. Based on this, we have done the following:1. The evolution behavior of graphynes and graphdiyne at high temperatures is systematically studied by means of molecular dynamics and based on the self-adapted molecular reaction-order potential--AIREBO potential. The results show that the single-layer graphne and graphdiyne will undergo three continuous phase transitions during the melting process. First, the single-layer graphye and gradiyne, respectively, began to transition from 2800 and 2500 K to the initial amorphous graphoene phase (AGP), which is simply referred to as the primary phase; then, the initial meeting gradually evolved into an amorphous graphene phase through a structural adjustment process, This process continues until the temperature is raised to a temperature of 3650 K. The amorphous graphenene meeting remains relatively stable until the temperature is further increased to about 5000 K; and finally, the amorphous gaphene meeting gradually turns into an approximately liquid state when the temperature is further increased above 5000 K. The severe shrinkage of the single-layer graphne and graphdiyne at high temperatures and the subsequent stretching play a decisive role in the process of forming the initial amorphous graphene phase. Unlike the well-known KTHY theory on the prediction of the melting of two-dimensional materials, we did not observe the iconic intermediate phase--the-----------------------the amorphous graphoene phase (AGP) in the process of temperature-raising of the single-layer graphyne and graphdiyne. Based on the first principle, we have studied the effect of the chemical modification of graphyne and graphdiyne on their structural stability by the chemical modification of hydrogen and hydroxyl functional groups (-OH) and the regulation effect on their electronic structures. (1) It is found that the zero point can play an important role in evaluating the stability of the hydrogenated graphyne. Based on the calculated formation rate, we have found that the graphyne hydrogenation configuration (named eHH) with only sp2-hybrid carbon atoms is more stable than the graphyne hydrogenation configuration (named eH) that adsorbs only one hydrogen atom on each carbon atom. But the relationship between the free energy and the temperature of Helmholtz shows that the eH is more stable than the eHH when the temperature is lower than 670 K. By calculating the phonon spectrum, we have determined that eH and eHH are kinetically stable hydrogenated graphyne configurations. It is of interest that the band gap characteristics of graphyne undergo a direct, indirect, to direct transition as the hydrogen atom coverage increases over the graphyne. (2) The low energy configuration and the electronic structure of graphye and graphdiyne modified by hydroxyl (-OH) were studied. In the low energy configuration of the high-density hydroxyl group modification, the hydroxyl functional groups on the adjacent large and hexagonal carbocyclic rings and the hexagonal carbon ring form a hand property structure due to the stabilizing effect of the hydrogen bond between the hydroxyl functional groups. The configuration of the carbon-carbon bonds in the graphyne and gram diyne as a single bond is not stable when the hydroxyl functional groups are fully saturated with the hydrogenated graphyne and graphdiyne configurations. The results also show that the hydroxyl functional groups can lead to magnetic properties in the system, but such magnetic properties can only be present in low hydroxyl coverage configurations. The hydroxyl group forming hydrogen bonds between the two hydroxyl functional groups makes the system generally not magnetic, because the magnetic moment caused by the two hydroxyl groups in the system is anti-ferromagnetic coupling. Based on the first principle, two new pore-like two-dimensional carbon allotype bodies, named Cy and Cz, are predicted, which have lower formation energy than graphdiyne. Molecular dynamics simulations show that Cy and Cz can still maintain their thermodynamic stability even if the temperature is above about 1000 K. Their poisson ratio shows that they have an anisotropic mechanical property. The calculation of the electronic structure shows that Cy is a metal and Cz is shown as a semiconductor. And Cz has an anisotropic conductivity, which shows the potential of Cz in the field of nano-electronic devices. They also have pore-like structures of specific size and regular distribution, and have the potential to be a new type of molecular sieve. Three-dimensional single-layer phosphorus-nitrogen (PN) materials with singular structures and properties are proposed based on the first principle. The two-dimensional single-layer phosphorus-nitrogen (PN) materials with singular structures and properties are named as P-PN, P-PN and P-PN, respectively. Both the I-PN and the P-PN have a curved configuration, and the P-PN shows the characteristics of the fold. Their novel configuration has a very high thermal dynamic stability and a strong anisotropy of the mechanical properties of the PN material of these single-atomic layers. They are both indirect band-gap semiconductors and their single-axis strain in the opposite direction has a high degree of sensitivity. The three single-layer PN materials are cut into nano-bands and exhibit a significant quantum-size effect. In particular, the saw-tooth nanoribbons of the p-pn exhibit a size-dependent ferromagnetic material. These important properties show the potential for their use in the field of nano-electronic devices. We also put forward the possible ways to synthesize these three kinds of PN single-layer phase from the theory, which is worth further study in the experiment. On the basis of the calculation of the phonon spectrum and the first principle molecular dynamics simulation at finite temperature, we have found a new type of tricle-shaped two-dimensional argenene, which is simply the structure of T-As. T-As and can still maintain the thermodynamic stability at higher temperatures. The energy stability of T-As can be compared with the previously reported chair-arsene (C-As) and more stable than that of the stirup-type arsene (S-As). Unlike C-As and S-As, a single-layer T-As is a direct band-gap semiconductor with an energy gap of 1.377 eV. Our results show that the electronic properties of T-As can be effectively controlled by stacking, strain and cutting, indicating the potential of application in the field of nano-electronic devices in the future. Moreover, by adsorbing hydrogen or fluorine atoms in a specific direction on the surface of the T-As, a nanobelt having a specific edge type and a width can be obtained, which is advantageous in that it is made into a nano-device.
【学位授予单位】：湘潭大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ127.11;TB383.1
本文编号：2482865
[Abstract]:The two-dimensional nano-material has many novel properties due to the limitation of the dimension, and has become the frontier field of material science research. Recently, the excellent properties of the two-dimensional V-group nano-material represented by the graphdiyne and the single-layer black-phosphorus are of great concern to the people, and with the development of the research, the great application potential is gradually displayed. In order to broaden the application field of the two kinds of materials, and to facilitate the design of the nano-devices based on them, it is necessary to study the physical properties of the graphene and the two-dimensional V-group nano-materials from a theoretical point of view. Based on this, we have done the following:1. The evolution behavior of graphynes and graphdiyne at high temperatures is systematically studied by means of molecular dynamics and based on the self-adapted molecular reaction-order potential--AIREBO potential. The results show that the single-layer graphne and graphdiyne will undergo three continuous phase transitions during the melting process. First, the single-layer graphye and gradiyne, respectively, began to transition from 2800 and 2500 K to the initial amorphous graphoene phase (AGP), which is simply referred to as the primary phase; then, the initial meeting gradually evolved into an amorphous graphene phase through a structural adjustment process, This process continues until the temperature is raised to a temperature of 3650 K. The amorphous graphenene meeting remains relatively stable until the temperature is further increased to about 5000 K; and finally, the amorphous gaphene meeting gradually turns into an approximately liquid state when the temperature is further increased above 5000 K. The severe shrinkage of the single-layer graphne and graphdiyne at high temperatures and the subsequent stretching play a decisive role in the process of forming the initial amorphous graphene phase. Unlike the well-known KTHY theory on the prediction of the melting of two-dimensional materials, we did not observe the iconic intermediate phase--the-----------------------the amorphous graphoene phase (AGP) in the process of temperature-raising of the single-layer graphyne and graphdiyne. Based on the first principle, we have studied the effect of the chemical modification of graphyne and graphdiyne on their structural stability by the chemical modification of hydrogen and hydroxyl functional groups (-OH) and the regulation effect on their electronic structures. (1) It is found that the zero point can play an important role in evaluating the stability of the hydrogenated graphyne. Based on the calculated formation rate, we have found that the graphyne hydrogenation configuration (named eHH) with only sp2-hybrid carbon atoms is more stable than the graphyne hydrogenation configuration (named eH) that adsorbs only one hydrogen atom on each carbon atom. But the relationship between the free energy and the temperature of Helmholtz shows that the eH is more stable than the eHH when the temperature is lower than 670 K. By calculating the phonon spectrum, we have determined that eH and eHH are kinetically stable hydrogenated graphyne configurations. It is of interest that the band gap characteristics of graphyne undergo a direct, indirect, to direct transition as the hydrogen atom coverage increases over the graphyne. (2) The low energy configuration and the electronic structure of graphye and graphdiyne modified by hydroxyl (-OH) were studied. In the low energy configuration of the high-density hydroxyl group modification, the hydroxyl functional groups on the adjacent large and hexagonal carbocyclic rings and the hexagonal carbon ring form a hand property structure due to the stabilizing effect of the hydrogen bond between the hydroxyl functional groups. The configuration of the carbon-carbon bonds in the graphyne and gram diyne as a single bond is not stable when the hydroxyl functional groups are fully saturated with the hydrogenated graphyne and graphdiyne configurations. The results also show that the hydroxyl functional groups can lead to magnetic properties in the system, but such magnetic properties can only be present in low hydroxyl coverage configurations. The hydroxyl group forming hydrogen bonds between the two hydroxyl functional groups makes the system generally not magnetic, because the magnetic moment caused by the two hydroxyl groups in the system is anti-ferromagnetic coupling. Based on the first principle, two new pore-like two-dimensional carbon allotype bodies, named Cy and Cz, are predicted, which have lower formation energy than graphdiyne. Molecular dynamics simulations show that Cy and Cz can still maintain their thermodynamic stability even if the temperature is above about 1000 K. Their poisson ratio shows that they have an anisotropic mechanical property. The calculation of the electronic structure shows that Cy is a metal and Cz is shown as a semiconductor. And Cz has an anisotropic conductivity, which shows the potential of Cz in the field of nano-electronic devices. They also have pore-like structures of specific size and regular distribution, and have the potential to be a new type of molecular sieve. Three-dimensional single-layer phosphorus-nitrogen (PN) materials with singular structures and properties are proposed based on the first principle. The two-dimensional single-layer phosphorus-nitrogen (PN) materials with singular structures and properties are named as P-PN, P-PN and P-PN, respectively. Both the I-PN and the P-PN have a curved configuration, and the P-PN shows the characteristics of the fold. Their novel configuration has a very high thermal dynamic stability and a strong anisotropy of the mechanical properties of the PN material of these single-atomic layers. They are both indirect band-gap semiconductors and their single-axis strain in the opposite direction has a high degree of sensitivity. The three single-layer PN materials are cut into nano-bands and exhibit a significant quantum-size effect. In particular, the saw-tooth nanoribbons of the p-pn exhibit a size-dependent ferromagnetic material. These important properties show the potential for their use in the field of nano-electronic devices. We also put forward the possible ways to synthesize these three kinds of PN single-layer phase from the theory, which is worth further study in the experiment. On the basis of the calculation of the phonon spectrum and the first principle molecular dynamics simulation at finite temperature, we have found a new type of tricle-shaped two-dimensional argenene, which is simply the structure of T-As. T-As and can still maintain the thermodynamic stability at higher temperatures. The energy stability of T-As can be compared with the previously reported chair-arsene (C-As) and more stable than that of the stirup-type arsene (S-As). Unlike C-As and S-As, a single-layer T-As is a direct band-gap semiconductor with an energy gap of 1.377 eV. Our results show that the electronic properties of T-As can be effectively controlled by stacking, strain and cutting, indicating the potential of application in the field of nano-electronic devices in the future. Moreover, by adsorbing hydrogen or fluorine atoms in a specific direction on the surface of the T-As, a nanobelt having a specific edge type and a width can be obtained, which is advantageous in that it is made into a nano-device.
【学位授予单位】：湘潭大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ127.11;TB383.1
【相似文献】
相关期刊论文 前2条
1 刘雪,骆定法,贺媛,孙德志;碳酸的动力学稳定性[J];大学化学;2002年05期
2 ;[J];;年期
相关会议论文 前3条
1 邓利;赵又群;;基于相平面的汽车动力学稳定性协调控制研究[A];第八届全国动力学与控制学术会议论文集[C];2008年
2 王美聪;陈刚;王军;徐元利;陈晓娟;余绍蓉;吴文凯;;ICF装置大型支撑结构的动力学稳定性设计[A];第19届全国结构工程学术会议论文集（第Ⅰ册）[C];2010年
3 马国军;吴承伟;;边界滑移对转子—轴承系统动力学稳定性的影响[A];庆祝中国力学学会成立50周年暨中国力学学会学术大会’2007论文摘要集（下）[C];2007年
相关博士学位论文 前1条
1 马双英;新型二维材料的热动力学稳定性及其电子结构的调控[D];湘潭大学;2016年
相关硕士学位论文 前4条
1 张勇;高速滑动轴承—转子系统动力学稳定性分析与试验验证[D];湘潭大学;2015年
2 王培;基于差动制动的汽车动力学稳定性控制策略研究[D];长沙理工大学;2010年
3 王前;基于非线性动力学的FSAE赛车侧向动力学稳定性研究[D];华南理工大学;2013年
4 张璋;基于流固耦合的叶片结构动力学稳定性研究[D];南京航空航天大学;2012年
，本文编号：2482865
本文链接：https://www.wllwen.com/kejilunwen/huaxuehuagong/2482865.html
