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Effect of Functionalization on Graphenic Surfaces in their Properties
Published in Esteban A. Franceschini, Nanostructured Multifunctional Materials Synthesis, Characterization, Applications and Computational Simulation, 2021
María del Carmen Rojas, M. Victoria Bracamonte, Martín Zoloff Michof, Patricio Vélez, Fernanda Stragliotto, Guillermina L. Luque
Given the size of the systems that are of interest from the application point of view, theoretical studies usually rely on DFT calculations. It is well known that DFT has serious difficulties in accounting for long-range interactions, such as the non-covalent interactions mentioned above. Therefore, in the present-day state-of-the-art computer modeling calculations the inclusion of some type of correction to describe these types of interactions is mandatory. Two of the most popular approaches are adding an empirical correction to the Kohn-Sham energy, such as Grimme’s DFT-D method (Grimme et al. 2010, Caldeweyher et al. 2017) or using a purpose-designed functional, such as some of the highly parameterized hybrid Minnesota functionals (Zhao et al. 2006, Zhao and Truhlar 2008). In fact, the graphene surface has become the prototypical testing ground for van der Waals correction methods.
Study of Properties of Nanostructures and Metal Nanocomposites on Their Basis
Published in Satya Bir Singh, Alexander V. Vakhrushev, A. K. Haghi, Nanomechanics and Micromechanics, 2020
A. Yu. Fedotov, Alexander V. Vakhrushev
The potential energy of the system (1) is determined by the modified embedded-atom method (MEAM). The theory of MEAM is derived by using density functional theory (DFT). DFT method is currently considered the most recognized approach to the description of the electronic properties of solids. In the embedded-atom method, the complete electron density is a linear superposition of spherically averaged functions. This disadvantage is eliminated in the modified embedded atom method.
Molecular Simulation of Porous Graphene
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2019
Ziqi Tian, Haoran Guo, Liang Chen, Chad Priest
All four of these terms are the functionals of electron density. The first three terms can be expressed by electron density explicitly and relate to most of the total energy. The fourth term, EXC, includes all the rest many-particle interactions. Although this term doesn't contribute much to the total energy, it determines the accuracy of KS equation. Its exact expression is unknown and has to be approximated. There have been several approximations which allow acceptable accuracy of certain calculated quantities, for instance, local density approximation (LDA), local spin-density approximation (LSDA), and generalized gradient approximations (GGA). From 1980s, tens of functionals have been developed to describe electronic structure of various systems. At the same time, there are lots of available software packages to perform DFT calculation on periodic system, such as Vienna Ab initio simulation package (VASP) (Kresse and Furth-muller 1996), Quantum ESPRESSO (Giannozzi et al. 2009), and CP2K (Hutter et al. 2014). Nowadays, DFT method has been a significant tool for the calculation of solid-state physics and quantum chemistry.
On the determination of stopping cross-sections in ion scattering in solids and deviations from standard models
Published in Radiation Effects and Defects in Solids, 2020
Mario Mery, Lin Chen, Jorge E. Valdés, Vladimir A. Esaulov
In order to obtain a realistic description of the ion-solid interaction one should take properly into account the crystal atomic structure, electronic valence band and the inhomogeneity of the electron density. In recent works we performed such a modelling of ion scattering, in which the electron density in pristine crystalline solids (Au (111), Au(100), Au(110), Ag (110)) and also oxidised silver (28) is determined through first principles calculations using tight-binding linear muffin tin orbitals (TB-LMTO) (29). This is based on the density functional theory (DFT) within the local density approximation (LDA) for the exchange and correlation potential. The calculation solves the Kohn–Sham (30) equations in a self-consistent way taking into account the spatial environment of the atoms. The electron densities obtained in this manner, agree with those derived from a linear augmented plane-wave full-potential (LAPW) calculations. As an example, Figure 2 shows the planar average (xy) charge density profile for reconstructed Au(110) and Au(111) surfaces and the spatial charge density profile below the first atomic layer of the Au(110) surface.
DFT study of electronic structure and optical properties of layered two-dimensional CH3NH3PbX3 (X=Cl, Br, I)
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Mahdi Faghihnasiri, Morteza Izadifard, Mohammad Ebrahim Ghazi
All DFT calculations were performed using Quantum ESPRESSO package (Giannozzi et al. 2009). Perdew–Burke–Ernzerhof of revised for solids (PBEsol) (Perdew et al. 2008) with projector-augmented plane-wave pseudopotentials (Blöchl 1994) were used for geometric optimization and electronic calculations. Norm-conserving pseudopotentials have been used for optical calculations. The electron configurations for C, N, H, Pb, Cl, Br, and I were [He] 2s2 2p2, [He] 2s2 2p3, 1s1, [Xe] 4f14 5d10 6s2 6p2, [Ne] 3s2 3p5, [Ar] 3d10 4s2 4p5, and [Kr] 4d10 5s2 5p5. The plane wave energy cutoff for geometric and electronic calculations was chosen as 45 Ry with 8 × 8 × 8 Monkhorst–Pack K-point sampling (Monkhorst and Pack 1976). For non-self-consistent calculation in density of state (DOS) analysis, Monkhorst–Pack K-point sampling was set as 15 × 15 × 15. The Gaussian smearing technique with 0.01 Ry smearing parameter has been used for DOS analysis. Also, the plane wave energy cutoff for optical calculations was chosen as 90 Ry with 8 × 8 × 8 Monkhorst–Pack K-point sampling. Full geometry optimizations were performed using the Broyden–Fletcher–Goldfarb–Shanno algorithm (Giannozzi et al. 2009), and atomic forces were converged to 0.001 eV/Å. In addition, the total energy in the electronic self-consistency loop was converged until the total energy reaches to less than 10−5 eV.
Isotope effects in liquid water via deep potential molecular dynamics
Published in Molecular Physics, 2019
Hsin-Yu Ko, Linfeng Zhang, Biswajit Santra, Han Wang, Weinan E, Robert A. DiStasio Jr, Roberto Car
Due to its quite favourable balance between accuracy and computational cost, density functional theory (DFT) [8–10] has emerged as the most commonly used electronic structure theory method during AIMD simulations of condensed-phase systems. While DFT is (in principle) an exact theory, the functional form of the exchange-correlation energy still remains unknown; as such, DFT (in practice) relies on an established hierarchy of approximations which allows for (semi-)systematic improvements in accuracy with a corresponding increase in the computational cost [11]. Previous studies have demonstrated that generalised-gradient approximation (GGA) based DFT functionals [12–14] – due to their propensity for self-interaction error [15] and lack of non-local correlation effects such as vdW dispersion interactions [16] – are inadequate for providing an accurate and reliable description of liquid water. Instead, it is more appropriate to use constraint-based meta-GGA functionals (such as SCAN [17–20]) or the class of more accurate vdW-inclusive hybrid functionals (such as PBE0-TS [1,21–26] or revPBE0-D3 [21,22,27–29]) when describing condensed-phase aqueous systems.