Imaging of the electron density distributions of hydrogen in LiH and LiOH by maximum entropy method

In order to explore the electron distribution of hydrogen, an electron density study was carried out by maximum entropy method (MEM) using the single crystal X-ray diffraction data of LiH measured by Vidal-Valat et al. [Acta Crystallogr. A48 (1992) 46-60] and those of LiOH measured by Gottlicher and Kieselbach [Acta Crystallogr. A32 (1976) 185-192]. It was found that the electron distribution of hydrogen in LiH is very spherical as a consequence of high symmetrical crystalline field. It was also recognized that there exists very weak covalent bond between lithium and hydrogen along the 〈100〉 direction. These features were consistent with the results of difference Fourier synthesis and multipole analysis by Vidal-Valat et al. Contrary to the LiH case, the position of hydrogen in LiOH was hardly assigned from the electron density map and only the contribution of hydrogen was recognized as a distortion of electron clouds of OH ellipse. The present study demonstrated that the electron distribution of hydrogen can be detected by MEM but it should be kept in mind that the distribution of electron from hydrogen was severely affected by the crystal field, which may result in the fact that the electron from hydrogen is far from a spherical distribution.