These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
MOF5_Manuscript.pdf (1.79 MB)
Quasi-Harmonic Lattice Dynamics of a Prototypical Metal-Organic Framework
Preprints are manuscripts made publicly available before they have been submitted for formal peer review and publication. They might contain new research findings or data. Preprints can be a draft or final version of an author's research but must not have been accepted for publication at the time of submission.
submitted on 08.05.2019 and posted on 09.05.2019by Matthew R. Ryder, Jefferson Maul, Bartolomeo Civalleri, Alessandro Erba
Quasi-harmonic lattice-dynamical calculations are performed to investigate the combined effect of temperature and pressure on the structural and mechanical properties of a prototypical metal-organic framework material: MOF-5. The softening upon compression of an A2g phonon mode at the gamma point in the high-symmetry Fm3m structure is identified, which leads to a symmetry reduction and a group subgroup phase transition to a low-symmetry Fm3 phase for compressions larger than 0.8%. The effect of the symmetry reduction on the equation-of-state of MOF-5 is investigated, which provides a static bulk modulus K reducing from 17 to 14 GPa and a corresponding change of K0 (pressure derivative of K) from positive to negative. The effect of pressure on the negative thermal expansion of the framework and on its mechanical response is analysed. The evolution of the mechanical anisotropy of MOF-5 as a function of pressure is also determined, which allows us to identify the occurrence of a shear-induced mechanical instability at 0.45 GPa.