Exploring water binding motifs to an excess electron via X (H O) [X = O, F]

X (H O) [X = O, F] is utilized to explore water binding motifs to an excess electron via ab initio calculations at the MP4(SDQ)/aug-cc-pVDZ + diffs(2s2p,2s2p) level of theory. X (H O) can be regarded as a water molecule that binds to an excess electron, the distribution of which is gauged by X . By varying the interatomic distance of X , r(X1-X2), the distribution of the excess electron is altered, and the water binding motifs to the excess electron is then examined. Depending on r(X1-X2), both binding motifs of C and C forms are found with a critical distance of ∼1.37 Å and ∼1.71 Å for O (H O) and F (H O), respectively. The energetic and geometrical features of O (H O) and F (H O) are compared. In addition, various electronic properties of X (H O) are examined. For both O (H O) and F (H O), the C binding motif appears to prevail at a compact distribution of the excess electron. However, when the electron is diffuse, characterized by the radius of gyration in the direction of the X bond axis with a threshold of ∼0.84 Å, the C binding motif is formed. © 2012 American Chemical Society.