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3 doped with different concentrations of cerium and nitrogen
Published in Domenico Lombardo, Ke Wang, Advances in Materials Science and Engineering, 2021
G.W. Pang, D.Q. Pan, C.X. Liu, L.Q. Shi, X.D. Wang, L.Z. Liu, J.B. Liu, L. Ma, L.L. Zhang, B.C. Lei
In the article, the first-principles method based on density functional theory (DFT) is used to calculate the electronic and structural properties by using CASTEP [24] software in Materials Studio 2017. The Perdew-Burke-Ernzerhof (PBE) [25] functional under the generalized gradient approximation (GGA) is chosen as the exchange correlation functional. K lattice points are selected in the Brillouin zone with 3 × 3 × 3 grid. The plane wave truncation energy Ecut is 410 eV, and the self-consistent convergence accuracy is 5.0 × 10–6 eV/atom. Here, the electronic configurations of five atoms are discussed: Na (2p63s1), Ta (5d36s2), O(2s22p6), Ce(4f15d16s2), and N(2s22p3). The space group of perovskite NOT is P12/M1 (No. 10). The experimental values of lattice constants [26] are a = c = 3.8895 Å,b = 3.8855 Å, α = γ = 90°, and β = 90.367°. Researchers have tested three kinds of large and small supercells [27] (2 × 2 × 2, 2 × 2 × 3, 3 × 3 × 3) all parameters were shown in Table 1:
Ab initio investigations of effect of sodium intercalation on the mechanical performance of graphitic cathode during aluminium electrolysis
Published in Canadian Metallurgical Quarterly, 2021
Wei Wang, Kai Sun, Weijie Chen
In the present work, the first-principles calculations were conducted out using the CASTEP code which is based on density functional theory (DFT). The electron–ion interactions were defined by ultrasoft pseudopotentials where generalised gradient approximation (GGA) was adopted for the exchange–correlation functional [11,12]. A minimum of 400 eV was chosen for the cutoff energy of plane wave. As illustrated in Figure 2, a single sodium atom and the 4 × 4 × 2 supercell graphene were constructed as the computational model of this work with 64 carbon atoms. The intercalant atom was placed at the centre of two layers of graphite. The lattice constant c was chosen large enough, as 7.6 Å, to neglect any interaction between two adjacent layers. The k-point samples were carried out by employing Monkhorst–Pack meshes of 3 × 3 × 3 grid with separation of 0.1 Å−1 in the reciprocal space. In the structural optimisation, the atoms were relaxed until the Hellmann–Feynman force and the total energy converged into 0.01 eV Å−1 and 10−3 ev/atom, respectively [12–15].
First-principles simulations on the structural, mechanical and thermodynamic properties of α, β, and h-CuGaO2
Published in Philosophical Magazine, 2019
Changwen Ye, Bing Liao, Rui Gong
All the first-principles calculations based on density functional theory (DFT) were implemented in CASTEP code [17]. The electronic exchange–correlation term was taken in generalised gradient approximation (GGA) [18] according to the Perdew–Burke–Ernzerhof for solids (PBEsol) [19]. The ultrasoft pseudopotentials were used and valence configurations 3d104s1 for Cu, 3d104s24p1 for Ga and 2s22p4 for O were performed as valence electrons, respectively. For β-CuGaO2, the Hubbard parameter U = 6.0 eV was used for Cu 3d electrons [14,16]. For geometry optimisation, the Brillouin zone sampling was performed with a 10 × 10 × 10, 5 × 4 × 5 and 10 × 10 × 3 k-point mesh. For elastic constants, a k-point mesh of 14 × 14 × 14, 6 × 5 × 6 and 12 × 12 × 4 was used for α-, β- and h-CuGaO2, respectively. The plane-wave cutoff energy was set at 850 eV for all calculations. The geometry optimisation was done by utilising the Brodyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm [20–23]. The energy convergence tolerance was 5 × 10−6 eV/atom. The maximum ionic displacement tolerance was 5 × 10−4 Å, the maximum stress tolerance was 2 × 10−2 GPa and the maximum force tolerance was 1 × 10−2 eV/Å.