(中南大學(xué) 化學(xué)化工學(xué)院，長沙 410083)
摘 要: 根據(jù)實驗晶格參數(shù)構(gòu)建3種不同類型氫氧化鋁——三水鋁石、拜耳石及諾耳石的晶體結(jié)構(gòu)模型，基于密度泛函理論(DFT)的廣義梯度近似(GGA)和局域密度近似(LDA)方法，用CASTEP程序分別對各研究體系進行幾何優(yōu)化，計算各體系的總能量、電子結(jié)構(gòu)、原子布居和鍵布居數(shù)。計算結(jié)果表明：在原子類型和數(shù)目相同的條件下，三水鋁石總能量最低，即最穩(wěn)定；GGA-PW91基組的能量效應(yīng)最高，在相同計算精度下，計算結(jié)果更收斂；GGA-PW91及LDA-CA-PZ基組水平的能帶結(jié)構(gòu)和態(tài)密度的計算結(jié)果表明，3種氫氧化鋁晶體能隙的最低值差別不明顯，但三水鋁石能隙的最高值比其他2種的低，從側(cè)面反映了三水鋁石的反應(yīng)活性可能稍高；布居分析結(jié)果表明，三水鋁石的H—O鍵和Al—O鍵的布居數(shù)最小，說明三水鋁石較拜耳石和諾耳石H—O鍵和Al—O鍵的結(jié)合力最小，理論上三水鋁石更有利于煅燒成氧化鋁。
關(guān)鍵字: 氫氧化鋁；密度泛函理論；電子結(jié)構(gòu)；布居分析
（College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China）
Abstract:Crystal structure models of Al(OH)3 crystals with three kinds of crystallines, which are gibbsite, bayerite and nordstradite, were built respectively according to the corresponding experimental crystal lattice. Geometry optimizations were implemented by CASTEP program module using general gradient approximation (GGA) and local density approximation (LDA) methods respectively based on density functional theory (DFT). The total energy, electronic structure, atomic and bond populations were also calculated. The calculation results of total energy indicate that gibbsite is more steady than the other two according to energy, and the effect of basis set of GGA-PW91 is the highest. Energy bond structure and density of states calculated at GGA-PW91 and LDA-CA-PZ levels show that the difference of energy gap ∆E (ELUMO−EHOMO) at the first group of BZ is not obvious, and that the highest value of ∆E of gibbisite is more lower than that of the other two Al(OH)3 crystals. Gibbisite may be more active than the other two crystals. The bond populations value of H—O and Al—O bonds of gibbisite is the smallest in three different Al(OH)3 crystals. This is to say that the combination force of H—O and Al—O bonds of gibbisite is the smallest and gibbisite may be more easier to be calcined into alumina theoretically.
Key words: Al(OH)3; DFT; electronic structure; population analysis
