Lattice Dynamics of Metal-Organic Frameworks (MOFs): Neutron Inelastic Scattering and First-Principles Calculations

摘要

By combining neutron inelastic scattering (NIS) and first-principlescalculations, we have investigated the lattice dynamics of MOF5. The structuralstability of MOF5 was evaluated by calculating the three cubic elasticconstants. We find that the shear modulus, c44 = 1.16 GPA, is unusually small,while two other moduli are relatively large (i.e. c11 = 29.42 GPa and c12 =12.56 GPa). We predict that MOF5 is very close to structural instability andmay yield interesting new phases under high pressure and strain. The phonondispersion curves and phonon density of states were directly calculated and oursimulated NIS spectrum agrees very well with our experimental data. Severalinteresting phonon modes are discussed, including the softest twisting modes ofthe organic linker.