Structure and Stability of VO2+ in Aqueous Solution: A Car-Parrinello and Static ab Initio Study
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- 作者：Aymeric Sadoc ; Sabri Messaoudi ; Eric Furet ; Ré ; gis Gautier ; Eric Le Fur ; Laurent le Pollè ; s ; Jean-Yves Pivan
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：June 11, 2007
- 年：2007
- 卷：46
- 期：12
- 页码：4835 - 4843
- 全文大小：177K
- 年卷期：v.46,no.12(June 11, 2007)
- ISSN：1520-510X
文摘
Quantum chemical calculations have been carried out to get some insight concerning the effects of temperatureand solvent acidity on the structure and stability of solvated VO2+ as the elementary chemical unit involved in thenucleation of vanadophosphates. First, because some recent theoretical studies have suggested a tendency ofdensity functional theory (DFT) to favor lower coordination numbers for such systems, static calculations havebeen performed on [VO2(H2O)(4-n)]+·nH2O (n = 0-2) conformers at the MP2 and DFT level of theory, using twodifferent combinations of basis sets. The results of two pure-GGA (BP86 and PBEPBE), two hybrid-GGA (PBE1PBEand mPWPW91), and two hybrid-meta-GGA (mPW1B95 and B1B95) functionals were analyzed on these systems.The comparison of the results indicates that the stability differences between the two methodologies are resolvedwhen hydration energy is taken into account, provided that some amount of HF exchange is introduced in the DFTcalculations. In a second step, Car-Parrinello simulations have been carried out starting from VO2(H2O)4+ surroundedby water molecules. The calculations at 300 K show the natural tendency of VO2(H2O)4+ to decompose to VO2(OH)2-and the requirements to work with an already acidified medium to be able to investigate the coordination sphereof VO2+ for an extended period of time. Under such conditions, we have obtained a clear preference for a five-coordinated vanadium. The molecular dynamics simulations performed at 500 K starting from hydrated VO2+ in aprotonated medium found VO(OH)3 to be the most stable structure, whereas this ideal candidate for oxolationreactions is expected to be a very minor species at room temperature.