Al-Ti-B合金中AlB2、TiB2和TiAl3的第一性原理研究

Al-Ti-B合金中AlB2、TiB2和TiAl3的第一性原理研究First principle study of AlB2, TiB2 and TiAl3 in Al-Ti-B alloy

采用基于密度泛函理論的第一性原理方法，研究0 K條件下Al-Ti-B體系中AlB2、TiB2和TiAl3的平衡晶格常數、形成熱、結合能及電子特性，并結合準簡諧德拜模型對3種物相在高溫條件下的熱力學基本性質進行了分析。計算結果表明：AlB2、TiB2和TiAl3的形成熱與結合能均為負值，表明3種相均具有結構穩定性，且穩定性由大到小依次為TiB2、TiAl3、AlB2；3種物相的離子性與金屬性由大到小依次為TiAl3、AlB2、TiB2，TiAl3與AlB2顯示離子鍵特性，而TiB2鍵合特性以共價鍵為主；3種物相的熱穩定性由大到小依次為TiB2、AlB2、TiAl3。計算所得TiB2、AlB2和TiAl3的熱力學性質可以用于分析氟鹽法制備Al-Ti-B時Al熔體與氟鹽之間反應發生情況以及中間合金最終的物相組成。

The crystal structure, heat of formation, cohesive energy and electronic properties of AlB2, TiB2 and TiAl3 in Al-Ti-B system under 0 K condition were investigated by using first principles based on density functional theory, and the quasi-harmonic Debye model was performed to calculate the thermodynamic properties of these phases. The results show that the heat of formation and cohesive energy of AlB2, TiB2 and TiAl3 are both negative, which indicate that these phases possess structural stability, and the structural stability decreases in the order from big to little of TiB2, TiAl3, AlB2. The iconicity and metallicity of these compounds increase in the following sequence from big to little of TiAl3, AlB2, TiB2, and the dominant bonding in TiAl3 and AlB2 is ionic, while the bonding in TiB2 is mainly covalent. The thermodynamic calculation results show that the thermal stabilities of the three phases decrease in the order from big to little of TiB2, AlB2, TiAl3, which can be used to illustrate the reactions between Al melt and fluoride salts when preparing Al-Ti-B by fluoride salt process.

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