Materials studio 2020

Simulation analysis based on the density functional theory (DFT) has been widely used to explain experimental phenomena. In order to study the sorption mechanism, sorption energy and sorption configuration were calculated by Materials Studio 2020 (BIOVIA, American). The exchange correlation function of the calculation process selects the PBE function under the generalized gradient approximation (GGA).

Plane-wave DFT calculations were performed using the CASTEP module within BIOVIA Materials Studio 2020 (ref. 95 ) using the single-crystal X-ray diffraction data for pon·HCl as an initial structural model. These calculations used the RPBE functional,^{96 (link)} ultrasoft pseudopotentials generated on-the-fly,^{97 (link)} a plane-wave cutoff energy of 800 eV, and a Monkhorst–Pack grid with a k-point spacing of 0.05 Å⁻¹.^{98 (link)} Structural refinements employed the LBFGS energy-minimizing scheme,^{99 (link)} with convergence thresholds including a maximum change in energy of 5 × 10⁻⁶ eV per atom, a maximum displacement of 5 × 10⁻⁴ Å per atom, and a maximum Cartesian force of 10⁻² eV Å⁻¹. Dispersion corrections were introduced using the semi-empirical two-body dispersion force field correction of Grimme (DFT-D2),^{100,101 (link)} or a reparametrized version of this method introduced by the authors for applications in NMR crystallography (DFT-D2*).^{102–104 (link)} These calculations used a two-step geometry optimization in which all atoms were first relaxed at the RPBE-D2 level (s₆ = 1.0; d = 20.0), followed by a second optimization in which only atoms involved in X–H⋯Cl⁻ (X = N, O) hydrogen bonding were relaxed at the RPBE-D2* level (s₆ = 1.0; d = 3.5), while all other atoms remained in fixed positions. This refined crystal structure was used in all subsequent computational analyses.

The model diagram of molecular rotation around azo group was created with a Materials Studio 2020 software²² (Biovia, San Diego, CA, US). To optimize the molecular structure, the generalized gradient approximation (GGA) proposed by Perdew et al.^{23 (link)} was used to perform density functional theory (DFT) calculations. The rotation model around azo group was created by using Conformers module in Materials Studio.