Hydrogen-rich superhydrides are promising high-Tc superconductors, with superconductivity experimentally observed near room temperature, as shown in recently discovered lanthanide superhydrides at very high pressures, e.g., LaH10 at 170 GPa and CeH9 at 150 GPa. Superconductivity is believed to be closely related to the high vibrational modes of the bound hydrogen ions. Here, we studied the limit of extreme pressures (above 200 GPa) where lanthanide hydrides with large hydrogen content have been reported. We focused on LaH16 and CeH16, two prototype candidates for achieving a large electronic contribution from hydrogen in the electron–phonon coupling. In this work, we propose a first-principles calculation platform with the inclusion of many-body corrections to evaluate the detailed physical properties of the Ce–H and La–H systems and to understand the structure, stability, and superconductivity of these systems at ultra-high pressure. We provide a practical approach to further investigate conventional superconductivity in hydrogen-rich superhydrides. We report that density functional theory provides accurate structure and phonon frequencies, but many-body corrections lead to an increase of the critical temperature, which is associated with the spectral weight transfer of the f-states.

Covalent self-assembly of molecules on crystal surfaces gives the promise of producing robust molecular networks. Recently [Floris, A. et al.et al., J. Am. Chem. Soc. 2016, 5837], a coupling reaction of tetra-(mesityl)porphyrin molecules on a Cu(110) surface was uncovered using scanning tunneling microscopy and ab initio density functional theory calculations. It was found that the molecules form clusters of covalently bound molecules with a specific C−H activation at the corners of the porphyrins facilitated by the surface. In this work, we employed the reaction mechanism proposed in the previous work to study the dynamics of growth of these covalent assemblies by means of the kinetic Monte Carlo method. We discuss the mechanism of growth and clusterization of molecules as well as the time evolution of desorbed hydrogen molecules that was previously measured by the temperature programmed desorption method.

No abstract