The Atomic Structure and Mechanical Properties of ZIF-4 under High Pressure: Ab Initio Calculations

Abstract

The effects of pressure on the structural and electronic properties and the ionic configuration of ZIF-4 were investigated through the first-principles method based on the density functional theory. The elastic properties, including the isotropic bulk modulus K, shear modulus G, Young’s modulus E, and Poisson’s ratio ν of the orthorhombic-type structure ZIF-4 were determined using the Voigt–Reuss–Hill averaging scheme. The results show that the ZIF-4 phase is ductile according to the analysis of K/G and Cauchy pressure. The Debye temperatures obtained from the elastic stiffness constants increase with increasing pressure. Finally, the pressure-dependent behaviors of the density of states and ionic configuration are successfully calculated and discussed.

Computation of Finite Temperature Mechanical Properties of ZIF Glasses by Molecular Dynamics

“…As shown on Table 2, we obtain a bulk modulus of K crystal = 1.39 GPa, in reasonable agreement with previous experimental 24,28,33 and computational [30][31][32] works. It is in the lower range of values (see Table 1), but further interpretation is limited, as the precise value determined depends on the computational methodology and -for experiments -also on subtle differences between MOFs from different batches or on the experimental setup.…”

“…pressure transmitting medium). 28,29 Additionally, computational values reported so far are either computed at 0 K [30][31][32] or performed at a low level of theory, 20,23 with no ab initio value at finite temperature reported in the literature for the ZIF-4 crystal.…”

“…Ab initio methods, and in particular density functional theory (DFT)-based methods, allow for a full description of the electronic state of physical systems at the quantum chemical level. They are commonly used to compute mechanical properties at 0 K using the stressstrain approach, 21 and have been applied to many MOFs, including for the ZIF-4 crystal [30][31][32] (see Table 1). Combining the precision of ab initio methods with molecular dynamics allows the determination of finite temperature mechanical properties and can account for potential phase transitions that may occur under the application of both temperature and pressure.…”

Computation of Finite Temperature Mechanical Properties of ZIF Glasses by Molecular Dynamics

“…pressure transmitting medium). 28,29 Additionally, computational values reported so far are either computed at 0 K [30][31][32] or performed at a low level of theory, 20,23 with no ab initio value at finite temperature reported in the literature for the ZIF-4 crystal.…”

“…Ab initio methods, and in particular density functional theory (DFT)-based methods, allow for a full description of the electronic state of physical systemsc at the quantum chemical level. They are commonly used to compute mechanical properties at 0 K using the stressstrain approach, 21 and have been applied to many MOF systems including for the ZIF-4 crystal [30][31][32] (see Table 1). Combining the precision of ab initio methods with molecular dynamics allows the determination of finite temperature mechanical properties and can account for potential phase transitions that may occur under the application of both temperature and pressure.…”