DFT Study of α-Keggin-type Iso-polyoxotungstate Anions [HWO] ( =1-4): Can [HWO] Exist?

The Keggin-type iso-polyoxotungstate (iso-POT) anions [HWO] 's, in which their central vacancies are occupied by protons, are attractive materials. It is of importance to reveal if the vacancies can be fully occupied by four protons. For further understanding the speciation of these iso-POT anions, relative stabilities and proton transfer reactions between H[HWO] and [HWO] were examined in detail by using the first-principles calculations (the nudged elastic band method, the synchronous transit-guided quasi-Newton method, the intrinsic reaction coordinate method, and frequency analysis calculations).