How flexible is the water molecule structure? Cambridge Structural Database and ab initio calculations study.

experimental for a free water molecule in the gas the bond angle (H – of ± 0.05° the bond (O–H) length of Neutron diffraction of the bond angle increases to 106.1 ± 1.8° and the bond length increases to 0.970 ± 0.005 of the bond angles in structures of ice have values close to a tetrahedral angle. in some of the ice structures, the bond and bond lengths remarkably deviates. Calculations on the spectroscopic potential energy surface showed the equilibrium structure of a water molecule with the bond angle of 104.501 ± 0.005° and the bond length of 0.95785 study, perfor an analysis of non-coordinated water containing structures archived in Cambridge Structural Database (CSD) as well as ab-initio calculations on a range of bond angles and bond lengths of water molecule. The results of the analysis of crystal structures solved by neutron as well as by X-ray diffraction analysis showed a large discrepancy of both the bond angle and bond length values. Namely, the ranges of the bond angl e and the average bond lengths of neutron solved structures having R factor ≤ 0.05 are from 100.74° to 113.92° and from 0.91 Å to 0.99 Å respectively. The corresponding range of the bond angle of X - ray solved structures is from 13.27° to 180.00°. High leve l ab initio calculations predicted a possibility for energetically low- cost (±1 kcal mol– 1) changes of both the bond angle and bond lengths in a wide range, from 96.4° to 112.8° (Fig. 1) and from 0.930 A to 0.989 A (Fig. 1), respectively . Consequently, it would lead to at least 15% of X-ray solved structures that contain questionable water molecule geometries.