目的 氨基酸是一类重要的环境友好型金属有机缓蚀剂,研究缓蚀剂分子在金属表面的吸附行为,对深入理解缓蚀机理及设计新型缓蚀剂分子有重要的理论意义.方法 基于第一性原理框架下的原子轨道线性组合方法,采用Dmol3软件研究了甘氨酸、丙氨酸和亮氨酸三种分子在铁表面的吸附行为.首先对铁晶体表面的形貌学参数进行了计算,然后选取合适的晶面作为吸附表面.最后通过计算三种分子在铁表面的吸附能和分波态密度等参数分析缓蚀机制.结果 铁的三种常见晶面中,Fe(110)面为最佳吸附表面.三种氨基酸分子在Fe(110)表面呈竖直型吸附构型,甘氨酸、丙氨酸和亮氨酸的吸附能绝对值大小分别为2.233、2.254、2.472 eV,这与其实验缓蚀效率大小顺序相一致.结论 缓蚀剂分子吸附可导致金属基底的功函数减小.Hirshfeld电荷分析表明,吸附过程中存在从氨基酸分子到Fe(110)表面的电子转移现象.态密度分析表明,氨基酸分子中的活性原子与铁表面原子形成了共价键,键能的大小对缓蚀剂分子的缓蚀效率起决定性作用.
Amino acids are environment friendly organic inhibitors for most metals. The study on adsorption behavior of inhibitor molecules on metal surfaces has profound theoretical significance in understanding the anticorrosive mechan-ism and designing novel corrosion inhibitors. Based on first principles approach, the adsorption behaviour of three amino acid molecules (i.e., glycine, alanine, and leucine) on iron surface was studied in linear combination of atomic orbitals method with the Dmol3 package. Firstly, the morphology parameters of iron crystal surface were calculated, and then a suitable crystal face was chosen as the adsorption surface. Finally, some parameters including adsorption energy and pro-jected density of states were calculated to explain the inhibition mechanism. The Fe(110) surface was an optimal simula-tion surface among the three common faces. Three molecules exhibited vertical adsorption structure on Fe(110) surface. The absolute values of adsorption energy were 2.233 eV, 2.254 eV, and 2.472 eV for glycine, alanine and leucine, respec-tively. The results were consistent with rank of experimental inhibition efficiency. The adsorption can reduce work func-tion value of Fe(110) substrate. The Hirshfeld charge analysis shows that there is an electronic transfer process from the inhibitors to Fe substrate in all chemisorbed configurations. The analysis of state density suggests that several covalent bonds are formed between active atoms and Fe surface atoms in amino acid molecules. Bond energy plays a decisive role in the inhibitive efficiency of corresponding inhibitors.
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