The anatase-rutile phase transformation of TiO(2) bulk material is investigated using a density functional theory (DFT) approach in this study. According to the calculations employing the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional with the Vanderbilt ultrasoft pseudopotential, it is suggested that the anatase phase is more energetically stable than rutile, which is in variance with the experimental observations. Consequently, the DFT + U method is employed in order to predict the correct structural stability in titania from electronic-structure-based total energy calculations. The Hubbard U term is determined by examining the band structure of rutile with various values of U from 3 to 10 eV. At U = 5 eV, a theoretical bandgap for rutile is obtained as 3.12 eV, which is in very good agreement with the reported experimental bandgap. Hence, we choose the DFT + U method (with U = 5 eV) to investigate the transformation pathway using the newly-developed solid-state nudged elastic band (ss-NEB) method, and consequently obtain an intermediate transition structure that is 9.794 eV per four-TiO(2) above the anatase phase. When the Ti-O bonds in the transition state are examined using charge density analysis, seven Ti-O bonds (out of 24 bonds in the anatase unit cell) are broken, and this result is in excellent agreement with a previous experimental study (Penn and Banfield 1999 Am. Miner. 84 871-6).
This is the first time the SnO2/PANI nanocomposite was utilized for the nitrogen oxide (NO)
photocatalytic degradation. In addition, the properties of the SnO2/PANI nanocomposite were deeply studied by various characterizations.
The results showed that the photostability of PANI has been improved
and the SnO2/PANI nanocomposite demonstrated the efficient
NO photocatalytic degradation. Notably, in this work, the adsorption
and photocatalytic mechanisms, polymer photodegradation, and the band
structure of the SnO2/PANI nanocomposite were fully and
systematically investigated via experimental measurements and density
functional theory (DFT).
The microscopic mechanism of the H2 adsorption of two Mg-MOF-74 isoreticular frameworks, one with a benzenedicarboxylate linker and the other with a dihydroxyfumarate linker, were studied on the basis of density functional theory (DFT) method.
Molecular dissociation of chlorine peroxide (ClOOCl), which consists of two elementary dissociation channels (of Cl-O and O-O), is investigated using molecular dynamics simulations on a neural network-fitted potential energy surface constructed by MP2 calculations with the 6-311G(d,p) basis set. When relaxed scans of the surface are executed, we observe that Cl-O dissociation is extremely reactive with a low barrier height of 0.1928 eV (18.602 kJ/mol), while O-O bond scission is less reactive (0.7164 eV or 69.122 kJ/mol). By utilizing the ''novelty sampling'' method, 35,006 data points in the ClOOCl configuration hyperspace are collected, and a 40-neuron feed-forward neural network is employed to fit approximately 90% of the data to produce an analytic potential energy function. The mean absolute error and root mean squared error of this fit are reported as 0.0078 eV (0.753 kJ/ mol) and 0.0137 eV (1.322 kJ/mol), respectively. Finally, quasi-classical molecular dynamics is executed at various levels of internal energy (from 0.8 to 1.3 eV) to examine the bond ruptures. The two first-order rate coefficients are computed statistically, and the results range from 5.20 to 22.67 ps -1 for Cl-O dissociation and 3.72-8.35 ps -1 for O-O dissociation. Rice-Ramsperger-Kassel theory is utilized to classically correlate internal energies to rate coefficients in both cases, and the plots exhibit very good linearity, thus can be employed to predict rate coefficients at other internal energy levels with good reliability.
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