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Density Functional Theory Studies for Catalysis of Atomically Precise Metal Clusters
Published in Yan Zhu, Rongchao Jin, Atomically Precise Nanoclusters, 2021
The accuracy of DFT calculations are quite remarkable, given the relatively low computational complexity [O(N3) to O(N4)] of DFT methods in comparison to higher level methods, such as the coupled cluster theory. Owing to error cancellation, DFT methods can predict catalytic reaction energies with small errors, typically a few kcal/mol, and are able to predict reasonable trends in catalysis. Among the DFT functionals, LDA is the simplest and least accurate, and thus it is not frequently used. DFT methods with GGA and hybrid functionals can accurately predict electronic structures and properties for various chemical systems, especially for chemical systems near equilibrium without strong electron correlations. Hybrid functionals are generally considered to be superior to GGA functionals, in terms of computational accuracy, but the trade-off is their much higher computational costs. PBE and B3LYP are the most widely used GGA and hybrid exchange-correlation functionals, respectively. The accuracy of DFT calculations is also dependent on other factors. A sufficiently large basis set that can better expand the wavefunction is necessary for accurate predictions. The inclusions of spin-orbit, relativistic, and dispersion corrections may also be critical for obtaining reliable prediction for more challenging chemical systems. Pseudopotentials are often required to reduce the size of basis sets and to include the relativistic effects in calculations. In the following, the commonly used DFT approaches in catalysis will be summarized.
First Principles Calculations in Exploring the Magnetism of Oxide-Based DMS
Published in Jiabao Yi, Sean Li, Functional Materials and Electronics, 2018
On the other hand, the Hybrid functionals like non-local Hartree-Fock scheme exchange can remedy the errors caused by derivative discontinuity. Typical hybrid functionals includes the HSE06, PBE0, HF, B3LYP, etc. They can pay respect to the occupation number which pulls the conduction band maximum down and describe the positions in conduction band correctly.
Heusler alloys for spintronic devices: review on recent development and future perspectives
Published in Science and Technology of Advanced Materials, 2021
Kelvin Elphick, William Frost, Marjan Samiepour, Takahide Kubota, Koki Takanashi, Hiroaki Sukegawa, Seiji Mitani, Atsufumi Hirohata
Topological insulators are one of the Dirac materials which have a topological nontrivial band structure leading to unique quantum phenomena [362]. For example, Qi et al. have studied on a topological insulator -Bi4I4 by applying high pressure in order to obtain the quasi-one-dimension [363]. Hybrid functional method has been used to calculate the electronic properties to prevent the underestimated band gap within the local density approximation or generalised gradient approximation. The simulations show a weak interaction between the along the AГYM path and strong dispersion along the BГ direction indicates a strong interaction within the chain. Therefore, quasi-1D characteristics of -Bi4I4 are confirmed. Density functional theory calculations show that electronic instability occurs at a critical pressure of 11.5 GPa. An experimental study on resistivity as a function of pressure shows a direct relationship between the resistivity and the bandgap stage (open or close). The resistivity decreases rapidly above the critical pressure and superconductivity is observed in -Bi4I4.
Accurate density functional prediction of molecular electron affinity with the scaling corrected Kohn–Sham frontier orbital energies
Published in Molecular Physics, 2018
DaDi Zhang, Xiaolong Yang, Xiao Zheng, Weitao Yang
The GGA methods such as the Becke–Lee–Yang–Parr (BLYP) [12,43] and the Perdew–Burke–Ernzerhof (PBE) [44] yield convex Ev(N + n) curves much like that of the LDA. Therefore, we thus apply the same form of correction for the LDA to the GGAs, i.e. ΔEGGAx ≈ ΔExLDA. A hybrid functional consists of both the Hartree–Fock (HF) and GGA exchange, and these two exchange components are corrected separately in GSC. For the B3LYP functional, we have ΔEB3LYPx ≈ (1 − a0)ΔELDAx + a0ΔEHFx with a0 = 0.20. The detailed form of ΔEHFx can also be found in Refs. [35,36].
On the impact of zero-point vibrations in calcium carbonate
Published in Phase Transitions, 2021
R. Belkofsi, G. Chahi, O. Adjaoud, I. Belabbas
We have demonstrated that among the three considered functionals, the best description of the zero-point vibrations is achieved by PBEsol. However, one may expect that comparable or better accuracy could be obtained by employing sophisticated and computationally demanding hybrid functionals. Among hybrid functionals, PBE0 and PBE0-DC are worth to be tested [38].