本文選題：Zr合金 + 結(jié)合能　； 參考：《遼寧大學(xué)》2017年碩士論文

【摘要】：Zr合金因具有非常好的耐腐蝕性,抗氧化性能,低的熱中子吸收截面積,以及較高的力學(xué)性能等一直被廣泛的應(yīng)用到核工業(yè)中。Nb擁有良好熱導(dǎo)率、較高的熔點和極強耐腐蝕性等特性,是很重要的合金元素,Nb作為鋯合金的合金化元素,能夠?qū)︿喓辖鹬挟a(chǎn)生的少量有害雜質(zhì)達到一定的清除作用,提高鋯合金抗腐蝕性,并可降低鋯合金的吸氫量,所以Nb非常適合做核反應(yīng)堆的合金化元素。對加入鋯合金中Nb的不同濃度及占位而言,研究其中腐蝕機制的影響,并研發(fā)新型Zr-Nb合金,模擬計算結(jié)果將對新型鋯鈮合金材料性能在微觀上的深刻認(rèn)識以及對各個領(lǐng)域的廣泛應(yīng)用與推廣都具有很大的參考價值和重要意義。本論文使用基于密度泛函理論的第一原理的VSAP軟件包,首先計算了Zr和Nb不同晶胞大小的結(jié)合能和電子結(jié)構(gòu),然后計算了Nb不同濃度及占位下Zr-Nb二元合金的晶體結(jié)構(gòu)和電子結(jié)構(gòu),最后計算了Zr、Nb晶體中雜質(zhì)三種近鄰下的相互作用能。重要結(jié)論如下:(1)在計算Nb不同濃度及占位下Zr-Nb二元合金的晶體結(jié)構(gòu)和電子結(jié)構(gòu)之前,分別計算了Zr晶體的2×2×2超胞和3×3×3超胞,以及Nb晶體的單胞和2×2×2超胞的晶格常數(shù)和結(jié)合能,計算結(jié)果與實驗值符合的很好。利用計算結(jié)果繪制了態(tài)密度圖。(2)Zr-Nb合金穩(wěn)定性:Zr-Nb合金晶格常數(shù)整體隨著Nb含量的增加呈現(xiàn)逐漸變小的趨勢,在Nb相同濃度且不同占位下的構(gòu)型中Zr14Nb2-(3)、Zr13Nb3-(1)、Zr12Nb4-(3)、Zr52Nb2-(2)、Zr51Nb3-(4)、Zr50Nb4-(5)穩(wěn)定性相對最好,即Zr-Nb合金中Nb元素更傾向于聚集分布;Zr-Nb合金電子結(jié)構(gòu):在Zr-Nb合金導(dǎo)帶、價帶以及費米能級處的電子結(jié)構(gòu)主要由Zr的d軌道和Nb的d軌道電子同時提供;耐腐蝕性最強的構(gòu)型為Zr14Nb2-(3)、Zr13Nb3-(3)、Zr12Nb4-(1)、Zr52Nb2-(2)、Zr51Nb3-(4)和Zr50Nb4-(7)。(3)向Zr晶體中摻雜Nb雜質(zhì)時,兩個原子之間表現(xiàn)出相互吸引,說明在Zr晶體中的Nb雜質(zhì)有聚集的趨勢;向Nb晶體中摻雜Zr雜質(zhì)時,兩個原子之間表現(xiàn)出相互吸引,且這種吸引力隨著距離的增大先增大后減小,從相互作用能的數(shù)值大小上看,這種相互作用的差異不是很明顯。
[Abstract]:Zr alloys have been widely used in nuclear industry because of their excellent corrosion resistance, oxidation resistance, low thermal neutron absorption area and high mechanical properties. Because of its high melting point and extremely strong corrosion resistance, Nb is an important alloying element of zirconium alloy, which can remove a small amount of harmful impurities produced in zirconium alloy and improve the corrosion resistance of zirconium alloy. It can reduce hydrogen absorption of zirconium alloy, so NB is very suitable for alloying element in nuclear reactor. For the different concentration and occupation of NB in zirconium alloy, the effect of corrosion mechanism was studied, and a new type of Zr-Nb alloy was developed. The simulation results will be of great reference value and significance to the microcosmic understanding of the new zirconium and niobium alloy material and the wide application and popularization of the new zirconium and niobium alloy materials in various fields. In this paper, the binding energy and electronic structure of Zr and NB cell size are calculated by using the first principle VSAP software package based on density functional theory (DFT). Then the crystal structure and electronic structure of Zr-Nb binary alloy with different NB concentration and occupation were calculated. Finally, the interaction energy of three kinds of impurity in ZrNb crystal was calculated. The important conclusions are as follows: (1) before calculating the crystal structure and electronic structure of Zr-Nb binary alloy with different NB concentrations and sites, the lattice constants and binding energies of 2 脳 2 脳 2 supercell and 3 脳 3 脳 3 supercell of Zr crystal and 2 脳 2 脳 2 supercell of NB crystal are calculated, respectively. The calculated results are in good agreement with the experimental values. According to the calculated results, the stability of Zr-Nb alloy is gradually decreasing with the increase of NB content. The stability of Zr-Nb alloy is relatively best in the same NB concentration and different sites. The stability of Zr14Nb _ 2-ZR _ (13) NB _ (3) and Zr _ (12) NB _ (3) Nb _ (2) and Zr _ (51Nb _ (3) O _ (4) Nb _ (4) B _ (50) NB _ (5) is relatively best. That is to say, the NB element in Zr-Nb alloy is more inclined to aggregate and distribute the electronic structure of Zr-Nb alloy. The electronic structure at the conduction band, valence band and Fermi level of Zr-Nb alloy is mainly provided by the d orbital of Zr and d orbital electron of NB. The most corrosion-resistant configurations are Zr14Nb _ 2-Nb _ (3) and Zr _ (13) NB _ (3) and Zr _ (52) NB _ (2-N) ~ (2 +) and Zr _ (50 NB _ (4) ~ (7) ~ (7) ~ (3) Zr crystals, which indicate that the NB impurities in Zr crystals tend to aggregate, and the NB impurities in Zr crystals tend to be aggregated when doped with NB impurity in Zr crystals, and when Zr is doped into Zr crystals, the two atoms exhibit a mutual attraction between the two atoms, which indicates that there is a tendency of aggregation of NB impurities in Zr crystals, and when Zr is doped in Zr crystals, the two atoms exhibit mutual attraction. The two atoms exhibit mutual attraction and the attraction increases first and then decreases with the increase of distance. From the value of the interaction energy the difference of the interaction energy is not obvious.
【學(xué)位授予單位】：遼寧大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.414

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