Charge transfer in hydrogen

Possible charge transfers in a single hydrogen molecule are discussed in connection with the energetic sequence and relation to transitions in high-pressure solid hydrogen. Transition pressure to atomic metallic hydrogen was estimated to about 8 +/- 1 Mbar, based on recent evaluation of the free energy of molecular hydrogen and the equation of state for the atomic metallic phase of hydrogen by Kagan et al. (Zh. Eksp. Teor. Fit. 73 (1977) 967). The size of the II ion as a function of pressure is discussed and a possible stepwise (quantized) ionization of the H-2 species in high pressures is formulated. The possibility of solution formation of covalent and ionic hydrogens is mentioned, and an example of a transition from covalent to ionic bond is given. (C) 1999 Elsevier Science B.V. All rights reserved.