Extension of the QuickFF force field protocol for an improved accuracy of structural, vibrational, mechanical and thermal properties of metal–organic frameworks

Abstract

QuickFF was originally launched in 2015 to derive accurate force fields for isolated and complex molecular systems in a quick and easy way. Apart from the general applicability, the functionality was especially tested for metal–organic frameworks (MOFs), a class of hybrid materials consisting of organic and inorganic building blocks. Herein, we launch a new release of the QuickFF protocol which includes new major features to predict structural, vibrational, mechanical and thermal properties with greater accuracy, without compromising its robustness and transparent workflow. First, the ab initio data necessary for the fitting procedure may now also be derived from periodic models for the molecular system, as opposed to the earlier cluster‐based models. This is essential for an accurate description of MOFs with one‐dimensional metal‐oxide chains. Second, cross terms that couple internal coordinates (ICs) and anharmonic contributions for bond and bend terms are implemented. These features are essential for a proper description of vibrational and thermal properties. Third, the fitting scheme was modified to improve robustness and accuracy. The new features are tested on MIL‐53(Al), MOF‐5, CAU‐13 and NOTT‐300. As expected, periodic input data are proven to be essential for a correct description of structural, vibrational and thermodynamic properties of MIL‐53(Al). Bulk moduli and thermal expansion coefficients of MOF‐5 are very accurately reproduced by static and dynamic simulations using the newly derived force fields which include cross terms and anharmonic corrections. For the flexible materials CAU‐13 and NOTT‐300, the transition pressure is accurately predicted provided cross terms are taken into account. © 2018 Wiley Periodicals, Inc.

Design, Parameterization, and Implementation of Atomic Force Fields for Adsorption in Nanoporous Materials

“…[460] The QuickFF force field protocol was extended for an improved accuracy of structural, vibrational, mechanical, and thermal properties of metal-organic frameworks like IRMOF-1, MIL-53(Al), CAU-13, and NOTT-300. [461] UFF4MOF [462,463] is an extension of the original Universal force field UFF (UFF) that incorporates additional atom types found in the Computation-Ready Experimental (CoRE) Database. [464] The BTW-FF model is a transferable inter-atomic potential that can be applied to MOFs regardless of metal or ligand identity.…”

Pillared-layered metal–organic frameworks for mechanical energy storage applications

“…To extend our predictions towards experimental conditions at higher temperature, we performed force eld MD simulations as described in the Methods section on DMOF-1(Zn) with a new QuickFF force eld 72,73 The Helmholtz free energy proles are shown in Fig. 4.…”

Unraveling the thermodynamic conditions for negative gas adsorption in soft porous crystals

“…The thermodynamic model requires input profiles for the empty host material (F host (V)), pore volume (V p (V)) and interaction energy (ΔU(V)) as well as van der Waals a and b parameters. For DUT-49, F host (V) was constructed with a newly developed force field using QuickFF 38,39 (more details can be found in Supplementary Note 3), ΔU(V) was computed by means of the Monte Carlo scheme outlined in ref. 37 using the Universal Force Field 40 for the van der Waals interactions and atomic charges derived using the Minimal Basis Iterative Stockholder (MBIS) method 41 to model the electrostatic interactions, and the pore volume was fitted to the experimental measurements from ref.…”

“…For MIL-53(Al) the free energy of the empty host was constructed using a QuickFF force field taken from ref. 39 , while the profiles for the adsorption energy and pore volume were computed using the scheme of ref. 37 with the same force field that was applied for the computation of the free energy profile (augmented with the MM3 parameters and MBIS gaussian charges for methane and carbon dioxide).…”