离子束技术是实现表面和近表面区域受控改性的极好方法，从而受到广泛的关注。当离子进入到材料中，会发生粒子间的相互作用，它能够改变靶物质的电荷分布，化学及物理特性，在材料科学、生物医学、核能和航天航空等领域提供了新的研究方法。带电粒子通过物质时，会引起电子的激发和跃迁，以及与原子核发生相互作用，导致沉积能量在物质中，从而产生能量耗散。前者被称为电子阻止本领，后者被称为核阻止本领。如果它们停止并停留在介质中，带电离子可以改变介质材料的元素组成（如果离子的组成与介质材料不同），从而会导致化学和物理变化。当高能离子撞击靶材料，高能级联碰撞可以破坏甚至摧毁介质的晶体结构，并且高能离子（MeV 数量级）可以引起核嬗变。

最近，对于低能离子在介质材料中的电子阻止本领的非线性行为、沟道效应和阈值效应等吸引了科研工作者的广泛兴趣。能量小于27\,keV/u的带电轻粒子（速度$v < 1\,a.u.$）在大多数介质材料中的电子阻止本领相对于速度表现为线性行为。本论文通过第一性原理计算关于低能$\alpha$-粒子沿沟道通过半金属HgTe晶体结构的研究发现电子阻止本领相对于速度表现为非线性行为，这是一个非常有趣的现象。此外，如果带电能量离子停留在介质中，会造成介质晶体结构缺陷，从而会引起材料性质的变化。主要工作有以下几方面：

一、使用TD-DFT模拟了弹核离子注入到拓扑半金属NbP和TaAs中的动力学随时间演化，有助于直观的给出晶体缺陷的形成过程。使用基态的DFT理论模型研究了离子停留在介质中的缺陷晶体结构，分析了产生不同点缺陷对费米能级附近外尔点的影响，从而间接讨论了点缺陷对半金属材料拓扑性的影响。空位缺陷会破坏材料的拓扑性，H$^+$(质子)和He$^{2+}$($\alpha$-粒子)的替位缺陷有一定的修复材料拓扑性能力，H$^+$和He$^{2+}$填隙缺陷结构会提升费米能级，并且缺陷都会导致简并能带结构的打开。同时计算了各种缺陷结构的形成能，可以发现间隙缺陷最为稳定，含有H$^+$粒子的取代位缺陷更容易形成，而含He$^{2+}$粒子的取代位点缺陷更难以形成。

二、基于第一性原理的TD-DFT模拟了轻弹核离子(包括H$^+$(质子)和He$^{2+}$($\alpha$-粒子)以及稍重的弹核离子C$^{4+}$ 沿$\left \langle100\right \rangle$，$\left \langle110\right \rangle$和$\left \langle111\right \rangle$沟道通过半金属HgTe的电子阻止行为。研究发现，弹核速度直到1.0\,a.u.，质子的电子阻止本领呈现很好的线性行为并且与半经验SRIM值符合的很好，而$\alpha$-粒子的电子阻止本领出现了有趣的非线性行为，这归因于相应弹核速度下不同的电荷转移现象。对于弹核离子C$^{4+}$，通过选择非沟道中心的不同碰撞参数，电子阻止本领曲线能够和半经验SRIM较好的吻合。通过定量的电荷转移研究了电子阻止本领的沟道效应；同时通过比较不同弹核在沟道中的电荷转移情况，发现弹核所带电荷数越多其发生的电荷交换幅度越大并且交换越活跃。

三、通过第一性原理的TD-DFT计算了H$^+$(质子)和He$^{2+}$($\alpha$-粒子)在窄带隙半导体Ge中的电子阻止本领，研究了其沟道效应及受碰撞参数的影响。拟合线性的电子阻止本领随弹核速度变化曲线，存在一个0.0276\,a.u.的阈值速度。基于DFT计算Ge 的能带结构间接带隙为0.935\,eV，弹核必须达到一定的动能才能将价带中的电子携带通过间接带隙，由此得到的阈值$v_{th} = 0.0292\,a.u.$。因此，发现这两个计算结果能够非常好的吻合，并且与实验值也能够很好的保持一致。

本论文的创新点有：
（1）理论上阐明了点缺陷对新型拓扑半金属材料性质的重要影响，通过分析电子能带结构验证了缺陷对拓扑性的改变。空位缺陷会破坏材料的拓扑性，H$^+$(质子)或He$^{2+}$($\alpha$-粒子)离子作为替位粒子会修复空位缺陷所破坏的拓扑性。
（2）研究低能轻离子在半金属材料中的电子阻止本领，发现定量的电荷交换是能量耗散的重要渠道。不同弹核的电子阻止本领与弹核所带电荷量相关。阐明了电子阻止本领的非线性行为归因于带电离子与介质原子之间的电荷转移。
（3）通过材料体电子能带结构的带隙分析了弹核在介质中电子阻止本领的阈值效应，本文通过TD-DFT得到的电子阻止本领的阈值与带隙计算的阈值和实验阈值都能非常好的吻合。提出了当入射离子穿过介质膜时，在电子带隙中，由入射离子引起的局域电子缺陷态像电梯一样将价带中的电子携带通过间接带隙。

Ion beam technology is an excellent method to achieve controlled modification of surface and near surface regions, which has attracted wide attention. When the ions enter the material, they will interact with particles, which can change the charge distribution, chemical and physical properties of the target material. It provides new research methods in the fields of materials science, biomedicine, nuclear energy and aerospace. When the charged particles pass through matter, they cause the excitation and transition of electrons, as well as the interaction with the nucleus, which leads to the deposition of energy in matter, which results in energy dissipation. The former is called the electron stopping energy, and the latter is called the nuclear blocking energy. If they stop and stay in the medium, the charged ions can change the elemental composition of the dielectric material (if the composition of the ions is different from that of the dielectric material), which can lead to the chemical and physical changes. As the high-energy ions impact the target material, the high-energy cascade collisions can destroy or even destroy the crystal structure of the medium, and the high-energy ions (MeV orders of magnitude) can cause nuclear transmutation.

Recently, the nonlinear behavior, channel effect and threshold effect of the electronic stopping power of the low energy ions in the medium materials have attracted wide interest of researchers. The electronic stopping power behaviors of the charged light particles with the energy less than 27\,keV/u ($v < 1\,a.u.$) in most the medium materials are linearly with respect to the ionic velocity. This work calculates the low-energy $\alpha$-particle passes through the semimetal crystalline HgTe along the channel by first-principles calculations, and finds the fact that the electronic stopping power presents the nonlinear behaviors with respect to the ionic velocity, which is a very interesting phenomenon. In addition, if the charged energy ions stay in the medium, it will cause the defects in the crystal structure of the medium, which will change the properties of the material. The main works are as follows:

At first, using TD-DFT to simulate the dynamics process of the projectile ions in the topological semimetal NbP and TaAs, it is helpful to visualize the formation process of crystal defects. The DFT model of the ground state is employed to study the defect in the medium, and the influence of the defect at different points on the extrinsic point near the Fermi level is analyzed, which indirectly discusses the effect of the point defect on the topology of the semi-metallic material. The vacancy defects can destroy the topological properties of the material. the H and He particle substituted defects have a certain ability to repair the topological properties of the material. the H$^+$(proton) and He$^{2+}$($\alpha$-particle) interstitial doping defects can raise the fermi level, and the defects will lead to the opening of the degenerate band structure. The formation energy of various defect structures is also calculated. It can be found that the interstitial doping defect is the most stable, the substitute site defect containing H$^+$ particle is easier to form, and the substitute site defect containing He$^{2+}$ particle is more difficult to form.

Secondly, the electronic stopping power of the light ions (H$^+$(proton) and He$^{2+}$($\alpha$-particle)) and the projectile ion C$^{4+}$ in the semimetal HgTe along the $\left \langle100\right \rangle$, $\left \langle110\right \rangle$ and $\left \langle111\right \rangle$ channels are investigated by means of the TD-DFT model. The electronic stopping power of the H$^+$ shows a good linear behavior up to 1.0\,a.u., and accords well with the semi-empirical SRIM value, while the electronic stopping power of the He$^{2+}$ shows an interesting nonlinear behavior, which is attributed to the different charge transfer phenomenon at the corresponding projectile velocity. For the projectile ion C$^{4+}$, by selecting different the impact parameters in the non-channel center, the electronic stopping power is in agreement with the semi-empirical SRIM value. The channeling effect of electronic stopping power is researched by calculating quantitatively the charge transfer. The projectile ion with more charge can capture more electrons from the medium, the corresponding charge exchange amplitude is larger and the exchange phenomenon is more active.

Finally, the electronic stopping power of H$^+$(proton) and He$^{2+}$($\alpha$-particle) in the narrow band gap semiconductor Ge is calculated by the TD-DFT based on first-principles; the channeling effect and the impact parameters effect are studied. Fitting the linear electron stopping power, there is a threshold velocity of 0.0276\,a.u.. The indirect band gap of the semiconductor Ge from the DFT method is 0.935\,eV, only when the projectile reaches a certain kinetic energy, it can carry the electrons from the valence band to the conduction band (passing through the indirect band gap), the threshold value obtained from this band gap is $v_{th} = 0.0292\,a.u.$. In additions, these calculated results are found to be in good agreement with the experimental data.

The innovations of this paper list in that：
(1) The important influence of point defects on the properties of new topological semi-metal materials is studied, and the change of topological property is found by analyzing the electronic band structure. The vacancy defect can destroy the topological property of the semi-metal material, but H$^+$(proton) or He$^{2+}$($\alpha$-particle) as a substitute site particle is able to repair the topological property destroyed by the vacancy defect.
(2) Study on the electronic stopping power of light slow ions in semi-metallic materials, it is found that the quantity charge exchange is an important channel for electronic energy dissipation. The electronic stopping power of different projectiles is related to the amount of charge they carry. The nonlinear behavior of the electronic stopping power is attributed to the charge transfer between the projectile ion and the medium atoms.
(3) The threshold effect of the electronic stopping power is analyzed by the band gap of the electronic band structure of the material bulk. The threshold of the electronic stopping power obtained by TD-DFT is in good agreement with the threshold calculated by the band gap and the experimental threshold. It is proposed that when the incident ion passes through the medium film, in the electronic band gap, the localized electronic defect state caused by the incident ion carries the electrons in the valence band through the indirect band gap like an elevator.