【摘要】：在硅團簇中摻雜稀土金屬元素不僅可以提高硅團簇的穩(wěn)定性,還可以表現(xiàn)出磁性等新的性質(zhì)。稀土金屬-硅團簇可以作為新的功能材料的構(gòu)建單元,在新材料設(shè)計領(lǐng)域中有著極為重要的價值。本文采用不同的密度泛函方法,分別系統(tǒng)地研究了稀土金屬鐠摻雜的硅團簇Pr Si_n(n=3 9)及其陰離子和Pr Si_n(n=10 21)中性分子的結(jié)構(gòu)和性質(zhì)。在B3LYP,PBE0和m PW2PLYP水平下結(jié)合aug-SEG/ECP基組,對Pr Si_n(n=3 9)中性分子及其陰離子的幾何結(jié)構(gòu)和性質(zhì)如絕熱電子親和能,模擬的光電子能譜,穩(wěn)定性,HOMO-LUMO能隙,電荷轉(zhuǎn)移和磁性進行了詳細研究。研究結(jié)果表明含有MP2相關(guān)函的雙雜合m PW2PLYP方法可以準確地預測Pr原子摻雜硅團簇的基態(tài)結(jié)構(gòu)和性質(zhì),具體結(jié)果如下:(1)從n=7開始,Pr Si_n(n=3 9)陰離子團簇的基態(tài)結(jié)構(gòu)不屬于取代結(jié)構(gòu)。中性的基態(tài)結(jié)構(gòu)結(jié)合一個電子后,基態(tài)結(jié)構(gòu)中額外的電子效應(yīng)非常強烈。Pr Si3-,Pr Si6-和Pr Si8-團簇的基態(tài)結(jié)構(gòu)不同于其中性團簇。(2)預測的Pr Si_n(n=3 9)的電子親合能的平均絕對誤差僅為0.05 e V。最大誤差為0.10 e V。(3)實驗的光電子能譜與理論模擬結(jié)果一致,表明預測的Pr Si_n-(n=4 9)團簇的基態(tài)結(jié)構(gòu)是可信的。(4)根據(jù)模擬光電子能譜和理論計算的電子親合能,我們重新分配了PrSi_4~-的實驗光電子能譜,得到了PrSi_4~-電子親合能的實驗值為2.0±0.1 e V,不是1.6±0.1 e V。(5)計算了從Pr Si_n斷裂出Pr原子的斷裂能。(6)HOMO-LUMO能隙表明摻雜稀土原子能明顯提高硅團簇的光化學反應(yīng)性,但提高的光化學反應(yīng)性效應(yīng)不如Eu和Sm原子摻雜在硅團簇中的好。(7)自然布居分析表明中性Pr Si_n及其陰離子中(除Pr Si3外)其4f電子參與成鍵,但Pr原子的磁性沒有消失,Pr Si_n的大部分磁性由Pr原子提供。在B3LYP和PBE0水平下結(jié)合SEG/ECP基組,系統(tǒng)地研究了Pr Si_n(n=10 21)中性分子的幾何結(jié)構(gòu)和性質(zhì)。研究結(jié)果表明:(1)由Si原子的cc-p VTZ和cc-p VDZ基組進行構(gòu)型優(yōu)化后獲得的基態(tài)結(jié)構(gòu)相同。(2)從n=20開始,Pr Si_n基態(tài)結(jié)構(gòu)預測為內(nèi)嵌的籠形結(jié)構(gòu),即Pr Si20為Pr Si_n最小籠型基態(tài)結(jié)構(gòu)。(3)穩(wěn)定性分析的結(jié)果表明Pr Si11,Pr Si13,Pr Si16和Pr Si20比其它團簇更穩(wěn)定,特別是Pr Si20構(gòu)型。(4)HOMO-LUMO能隙分析表明,在純Si_n(n=10 21)團簇中摻雜Pr原子可提高團簇的光化學敏感性,尤其是Pr Si20結(jié)構(gòu)。(5)電荷轉(zhuǎn)移和磁性分析可以看出,Pr Si_n的大部分磁性由Pr原子提供,形成籠形結(jié)構(gòu)時磁性并沒有消失。Pr原子的4f電子參與成鍵,它的一個電子從4f軌道轉(zhuǎn)移到5d軌道。在非籠形團簇中,Pr原子是電子供體;當形成籠形結(jié)構(gòu)時,Pr原子是電子受體。Pr Si20結(jié)構(gòu)中的Pr原子與硅團簇之間的成鍵性質(zhì)本質(zhì)上為離子鍵,且成鍵作用非常強。
[Abstract]:Doping rare earth elements into silicon clusters can not only improve the stability of silicon clusters, but also exhibit new properties such as magnetic properties. Rare earth metal-silicon clusters can be used as building units of new functional materials, which are of great value in the field of new materials design. In this paper, the structure and properties of praseodymium doped silicon clusters (Pr Si_n (nd3) 9) and their anions and neutral molecules (Pr Si_n (nn10 / 21) have been systematically studied by using different density functional methods (DFT). The geometric structure and properties of neutral molecules and their anions of Pr Si_n (nun3 + 9) have been studied in detail at the level of B3LYPX PBE0 and m PW2PLYP, such as adiabatic electron affinity, simulated photoelectron spectroscopy, stability, HOMO-LUMO gap, charge transfer and magnetism. The results show that the double hybrid m PW2PLYP method with MP2 correlation function can accurately predict the ground state structure and properties of Pr atom doped silicon clusters. The results are as follows: (1) the ground state structure of Pr Si_n (nni3 + 9) anion cluster does not belong to the substitution structure. When the neutral ground state structure binds to one electron, the extra electron effect in the ground state structure is very strong. The ground state structure of Pr Si3-,Pr Si6- and Pr Si8- clusters is different from that of their neutral cluster. (2) the average absolute error of the predicted electron affinity energy of Pr Si_n (NN3 + 9) is only 0. 05 EV. The maximum error is 0.10 e V. (_ 3) the photoelectron spectroscopy of the experiment is consistent with the theoretical simulation results, which indicates that the predicted ground state structure of the Pr Si_n- (nni4) cluster is credible. (4) the electron affinity energy calculated according to the simulated photoelectron spectroscopy and the theoretical calculation. We've reallocated PrSi_4~- 's experimental photoelectron spectroscopy, The experimental value of PrSi_4~- electron affinity energy is 2. 0 鹵0. 1 EV, not 1. 6 鹵0. 1 e V. (5. The fracture energy of Pr atom is calculated from Pr Si_n. (6) the HOMO-LUMO gap shows that doped rare earth atomic energy can obviously improve the photochemical reaction of Si cluster. But the enhanced photochemical reactivity effect is not as good as that of Eu and Sm atoms doping in silicon clusters. (7) Natural population analysis shows that 4f electrons in neutral Pr Si_n and its anions (except Pr Si3) participate in bonding. But the magnetism of the Pr atom has not disappeared, and most of the magnetism of the Pr Si_n atom is provided by the Pr atom. The geometric structure and properties of neutral molecules of Pr Si_n (n ~ (10) ~ (21) have been systematically studied at the level of B3LYP and PBE0 combined with the SEG/ECP basis set. The results show that: (1) the ground state structure obtained by the configuration optimization of the cc-p VTZ and cc-p VDZ basis sets of Si atoms is the same. (2) starting from NW 20, the ground state structure of Pr Si_n is predicted to be an embedded cage structure. That is, Pr Si20 is the smallest cage ground state structure of Pr Si_n. (3) the results of stability analysis show that Pr Si11,Pr Si13,Pr Si16 and Pr Si20 are more stable than other clusters, especially the Pr Si20 configuration. (4) the band gap analysis of HOMO-LUMO shows that, Doping of Pr atoms in pure Si_n (nni10 ~ (21) clusters can enhance the photochemical sensitivity of the clusters, especially the Pr Si20 structure. (5) charge transfer and magnetic analysis show that most of the magnetic properties of Pr Si_n are supplied by Pr atoms. The magnetic properties do not disappear when the cage structure is formed. The 4f electrons of the Pr atom take part in bonding, and one of its electrons is transferred from the 4f orbital to the 5d orbital. In non-caged clusters, the Pr atom is an electron donor, while the Pr atom is an electron receptor when the cage structure is formed. The bonding property between the Pr atom and the silicon cluster in the Pr Si20 structure is essentially ionic bond, and the bonding effect is very strong.
【學位授予單位】：內(nèi)蒙古工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O641.1

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1 白燕枝;趙高峰;沈?qū)W鋒;孫建敏;王淵旭;;TbSi_n(n=2-13)團簇的結(jié)構(gòu)、電子及磁學性質(zhì)(英文)[J];物理化學學報;2011年01期

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本文編號：2284959