Ganduglia-Pirovano M Veronica, Sauer Joachim
Institut für Chemie, Arbeitsgruppe Quantenchemie, Humboldt Universität zu Berlin, Unter den Linden 6, D-10099 Berlin, Germany.
J Phys Chem B. 2005 Jan 13;109(1):374-80. doi: 10.1021/jp046233k.
The defect-free gamma-V(2)O(5)(001) surface and ordered structures of oxygen vacancies have been studied for a wide range of defect concentrations, Theta ((1)/(6) monolayer (ML) < or = Theta < or = 1 ML), combining density functional theory and statistical thermodynamics. The gamma polymorph of V(2)O(5) is characterized by two structurally different vanadium sites, V(A) and V(B). The V(A) sites having a weaker bond to an adjacent crystal layer are easier to reduce. Up to (1)/(2) ML, the V(A) defect structures with defects aligned along the [010] direction are increasingly more stable as in alpha-V(2)O(5)(001). At higher defect concentrations, the different coordination of the V(B) vanadium atoms at the gamma-V(2)O(5) surface causes an increase in the vacancy formation energy of approximately 0.8 eV/atom at Theta = 1.0 compared to Theta = (1)/(2). For alpha-V(2)O(5), this increase amounts to 0.2 eV/atom only. Under conditions (low oxygen partial pressures and high temperatures) at which the alpha-V(2)O(5)(001) surface would be fully reduced, the gamma-V(2)O(5)(001) surface is only partially reduced. The presence of surface vanadyl oxygen groups at V(B) sites may change the surface reactivity compared to that of alpha-V(2)O(5)(001).
结合密度泛函理论和统计热力学，研究了无缺陷的γ-V₂O₅(001)表面以及各种缺陷浓度（θ，1/6单层（ML）≤θ≤1 ML）下有序的氧空位结构。V₂O₅的γ多晶型由两个结构不同的钒位点V(A)和V(B)表征。与相邻晶体层键合较弱的V(A)位点更容易被还原。直至1/2 ML，与α-V₂O₅(001)中情况一样，缺陷沿[010]方向排列的V(A)缺陷结构越来越稳定。在更高的缺陷浓度下，γ-V₂O₅表面V(B)钒原子的不同配位导致与θ = 1/2相比，在θ = 1.0时空位形成能增加约0.8 eV/原子。对于α-V₂O₅，这种增加仅为0.2 eV/原子。在α-V₂O₅(001)表面将被完全还原的条件（低氧分压和高温）下，γ-V₂O₅(001)表面仅被部分还原。与α-V₂O₅(001)相比，V(B)位点处表面钒氧基的存在可能会改变表面反应性。
