scholarly journals First-Principles Study on the Mechanism of Greenhouse Gas Generation in Aluminum Electrolysis

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1118
Author(s):  
Kena Sun ◽  
Jie Li ◽  
Hongliang Zhang ◽  
Tianshuang Li ◽  
Jiaqi Li
Keyword(s):  
Greenhouse Gases ◽  
First Principles ◽  
Aluminum Electrolysis ◽  
First Principles Calculation ◽  
Anode Surface ◽  
Gas Generation ◽  
Good Accordance ◽  
Calculation Results ◽  
Complex Anions ◽  
Formation Paths

Greenhouse gases emitted by the aluminum electrolysis industry have brought great challenges to environmental protection. To address this problem, understanding the micro-generation mechanism of greenhouse gases in the electrolysis process is of great significance to their source suppression. Based on the first principles calculation method, the formation paths of CO, CO2 and COF2 during normal electrolysis were obtained by studying the adsorption behavior of oxygen and fluorine complex anions (short for [O]2−, [F]−) on the anode surface in cryolite alumina molten salt. The calculation results indicate that the O and F atoms prefer to adsorb at bridge site 1 of Model A, with the adsorption energies of −4.82 eV and −3.33 eV. In the [O]2− priority discharge stage, Path 3 is the most likely path for CO2 generation, while in the [O]2−, [F]− co-discharge stage, Path 3 is the most likely path for COF2 generation. It is deduced that the thermal decomposition of COF2 at high temperature should account for the generation of CF4 with a low concentration of the so-called non-anode effect PFC (NAE-PFC). Experiments were also conducted to verify the calculation by disclosing the bonding information of C, O and F, which are in good accordance with the results calculated by the first principle.

Site Preference of Refractory Elements in Ni-Based Single-Crystal Superalloys Alloying with Ru: From First Principles

2012 ◽  
Vol 554-556 ◽  
pp. 3-12
Author(s):  
Jian Jun Cui ◽  
Fei Sun ◽  
Jian Xin Zhang
Keyword(s):  
Binding Energy ◽  
Single Crystal ◽  
First Principles ◽  
First Principles Calculation ◽  
Partial Density ◽  
Site Preference ◽  
Strengthening Effect ◽  
Mulliken Population ◽  
Calculation Results ◽  
Partitioning Behavior

A first principles calculation method was used to investigate the site preference of Ruthenium (Ru) at the γ/γ′ interface in Ni-based single-crystal superalloys. The calculation results show that the addition of Ru can decrease the total energy and the binding energy of γ/γ′ interface, which may result in an improved microstructure stability of Ni-based single-crystal superalloys. Moreover, by calculation, it is also found that Ru can stabilize both γ and γ′ phases and have a preference for Ni site at the coherent γ/γ′ interface. When Ru substitutes the central Ni at the γ/γ′ interface, a reverse partitioning of W, Re and Cr occurs; while the partitioning behavior of Mo is not affected. The influence of Ru on the partitioning behavior of W, Re and Cr in γ′-Ni3Al was studied by Dmol3 calculation as well. The calculation results show that W, Re and Cr have a preference for Ni site in γ′- Ni3Al with Ru alloying. When Ru substitutes the central Ni atom, the site preference of W, Re and Cr varies accordingly. Furthermore, electronic structure analysis of γ/γ′ interface and γ′-Ni3Al in terms of Mulliken population and partial density of states (PDOS) was performed to understand the alloying mechanism of Ru in Ni-based single-crystal superalloys. The results show that the strengthening effect of Ru alloying is mainly due to the reduction in binding energy of Ru as well as a p-orbital hybridization between Ru and the host atoms.

Investigation of Electronic Structures of F-Doped TiO2 by First-Principles Calculation

2009 ◽  
Vol 620-622 ◽  
pp. 647-650 ◽  
Author(s):  
Ying Cui ◽  
Hao Du ◽  
Li Shi Wen
Keyword(s):  
Photocatalytic Activity ◽  
First Principles ◽  
Electronic Structures ◽  
Lower Energy ◽  
Anatase Tio2 ◽  
First Principles Calculation ◽  
Visible Light Region ◽  
Doped Tio2 ◽  
Light Region ◽  
Calculation Results

F-doped TiO2 has exhibited superior photocatalytic activity. However, its electronic structures and photocatalysis mechanism are still unclear. In the present work, the structural optimization and electronic structure of F-doped anatase TiO2 have been investigated by means of the first-principles pseudopotential total energy method. It has been demonstrated that F doping would modify the valence band at the lower energy direction in the F-doped TiO2. Calculation results confirm that doping of fluorine would not shift the absorption edge into the visible light region. Instead, we attributed its photocatalytic activity to the enhancement of the oxidative power of F-doped TiO2.

scholarly journals Robust Spin-Gapless Behavior in the Newly Discovered Half Heusler Compound MnPK

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3117 ◽  
Author(s):  
Jiaxue You ◽  
Jieting Cao ◽  
Rabah Khenata ◽  
Xiaotian Wang ◽  
Xunan Shen ◽  
...  
Keyword(s):  
First Principles ◽  
Experimental Studies ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Good Resistance ◽  
Heusler Compound ◽  
New Class ◽  
Hubbard U ◽  
Calculation Results ◽  
Spin Gapless Semiconductors

Spin gapless semiconductors have aroused high research interest since their discovery and a lot of effort has been exerted on their exploration, in terms of both theoretical calculation and experimental verification. Among different spin gapless materials, Heusler compounds stand out thanks to their high Curie temperature and highly diverse compositions. Especially, both theoretical and experimental studies have reported the presence of spin gapless properties in this kind of material. Recently, a new class of d0 − d Dirac half Heusler compound was introduced by Davatolhagh et al. and Dirac, and spin gapless semiconductivity has been successfully predicted in MnPK. To further expand the research in this direction, we conducted a systematical investigation on the spin gapless behavior of MnPK with both generalized gradient approximation (GGA) and GGA + Hubbard U methods under both uniform and tetragonal strain conditions by first principles calculation. Results show the spin gapless behavior in this material as revealed previously. Different Hubbard U values have been considered and they mainly affect the band structure in the spin-down channel while the spin gapless feature in the spin-up direction is maintained. The obtained lattice constant is very well consistent with a previous study. More importantly, it is found that the spin gapless property of MnPK shows good resistance for both uniform and tetragonal strains, and this robustness is very rare in the reported studies and can be extremely interesting and practical for the final end application. This study elaborates the electronic and magnetic properties of the half Heusler compound MnPK under uniform and tetragonal strain conditions, and the obtained results can give a very valuable reference for related research works, or even further motivate the experimental synthesis of the relative material.

scholarly journals Thermodynamic properties of 2H-MoSe2 from first principles quasi-harmonic approximation

2020 ◽  
Vol 21 (3) ◽  
pp. 478-485
Author(s):  
O. Vasiliev
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Harmonic Approximation ◽  
Formation Enthalpy ◽  
First Principles Calculation ◽  
Data Sets ◽  
Calculation Results ◽  
Satisfactory Approximation

In this paper, we report the results of first-principles calculation of 2H-MoSe2 thermodynamic properties within the quasi-harmonic approximation. The focus of the article is on the temperature dependencies of the heat capacity up to 1000 ℃ and values of enthalpy of formation, enthalpy, and entropy at 298,15 K, and their comparative analysis with the existing experimental data. The results show good general agreement with the published experimental data sets allowing to use them as arbitration of existing discrepancies. Increasing deviations of the heat capacity above the room temperature suggest that factors not included in the quasi-harmonic approximation, such as vibrational anharmonicity, may have a significant influence on the thermodynamics of 2H-MoSe2 in this temperature region. Considering the inconclusive high-temperature data from the experiment, the present results may be recommended as a satisfactory approximation until the appearance of more reliable experimental data or calculation results, taking into account more finite-temperature effects.

Luminescent properties and first-principles calculations of (Cr,Ca):YAG crystals

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744070
Author(s):  
Yan Wan ◽  
Meiyu Li ◽  
Erjuan Xie ◽  
Shoulei Xu ◽  
Yuyang Huang ◽  
...  
Keyword(s):  
First Principles ◽  
Luminescent Properties ◽  
Optical Bandgap ◽  
Experimental Results ◽  
First Principles Calculation ◽  
First Principles Calculations ◽  
Floating Zone ◽  
Charge Balance ◽  
Occupied State ◽  
Calculation Results

The single crystals of YAG, Cr:YAG and (Cr,Ca):YAG were grown in an optical floating zone furnace. The experimental results show that the optical bandgap of the YAG, (Cr,Ca):YAG and Cr:YAG crystals is about 6.52, 6.31 and 5.50 eV, respectively. The optical bandgap of the (Cr,Ca):YAG crystal is smaller than YAG and larger than Cr:YAG. First-principles calculation results showed that the additions of Cr into YAG will give rise to the change of the electronic states. In a Cr:YAG crystal, the Cr[Formula: see text] impurity introduces a band of 3[Formula: see text] occupied state near the Fermi level, which significantly narrowed the bandgap of Cr:YAG. In a (Cr,Ca):YAG crystal, as the Ca[Formula: see text] ions substitute for the Y[Formula: see text] ions, some of the Cr[Formula: see text] ions will change into Cr[Formula: see text] ions due to the charge balance, which increased the bandgap of the (Cr,Ca):YAG crystal in comparison with that of the Cr:YAG crystal. The calculation is in agreement with the experimental results.

Influence of Mg2+ Substitution for Sn4+ on Electronic Structure and Optical Properties of SnO2

2019 ◽  
Vol 11 (10) ◽  
pp. 1387-1394 ◽  
Author(s):  
Haiying He ◽  
Zibin Wu ◽  
Yu Chen ◽  
Zhihao Yang ◽  
Minghuai Yu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Valence Band ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculation ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Calculation Results ◽  
Localization Behavior

First-principles calculation based on density functional theory (DFT) were employed to theoretically study the influence of partially replacing Sn4+ by Mg2+ on the electronic structure and optical properties of SnO2. The calculation results revealed that the Femi level shifted into the valence band, thereby indicating a p-type conductivity character. The energy band gap for SnO2 was found to be narrowed due to Mg2+ doping. Considering that the energy level for Mg 3s orbitals is comparable to that of O 2p orbitals, the localization behavior in the SnO2 valence band was modified. The imaginary part of dielectric functions' spectrum shifted towards lower energy after doping SnO2 with Mg2+, accompanied by an obvious redshift of the absorption edge. Furthermore, the absorption intensity for the doped systems was larger than that of pure SnO2 matrix in the low-energy region.

Molar Volume of Fcc Phase in the Ni-Cr-Mo System

2014 ◽  
Vol 936 ◽  
pp. 1209-1215 ◽  
Author(s):  
Jin Cai Li ◽  
Xiao Gang Lu ◽  
Yan Lin He
Keyword(s):  
Experimental Data ◽  
Molar Volume ◽  
Solid Solutions ◽  
First Principles ◽  
First Principles Calculation ◽  
Calphad Approach ◽  
Volume Data ◽  
Calculation Results ◽  
Fcc Phase ◽  
Reasonable Description

The molar volume of fcc phase in the Ni-Cr-Mo system has been evaluated by means of the CALPHAD approach based on experimental data from the literature. The molar volumes of the non-stable fcc Cr and Mo were determined by extrapolating volume data from several stable solid solutions combined with the first-principles calculation results. A set of parameters has been obtained and can give a reasonable description of most experimental data on molar volume.

First-Principles Calculation of Al-Cu-Mg Alloy Strengthening Phase

2015 ◽  
Vol 1096 ◽  
pp. 109-113
Author(s):  
He Ma ◽  
Li Jia Chen ◽  
Lian Quan Guo ◽  
Li Leng ◽  
Lin Lin
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Heat Of Formation ◽  
First Principles Calculation ◽  
Mg Alloy ◽  
First Principles Calculations ◽  
Strengthening Phase ◽  
Functional Theory ◽  
Calculation Results ◽  
Mg Content

In this study, equilibrium lattice parameters, heat of formation and cohesive energy of four kinds of typical phases with different structure intermetallic compound in Al-Cu-Mg alloy were investigated by first-principles calculations based on density functional theory via CASTEP software. The calculation results are analyzed and show that ternary strengthening phase Al2CuMg generated first when Mg content is higher, while binary strengthening phase Al2Cu or Al3Cu2 first generated and more stable when Mg content is low in Al-Cu-Mg alloy which indicates that element Cu and Al alloying capacity significantly higher than that of Mg and Al element.

scholarly journals Crystallographic Characteristic Effect of Cu Substrate on Serrated Cathode Dissolution in Cu/Sn–3.0Ag–0.5Cu/Cu Solder Joints during Electromigration

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2486
Author(s):  
Wu Yue ◽  
Chao Ding ◽  
HongBo Qin ◽  
ChengGong Gong ◽  
JunXi Zhang
Keyword(s):  
First Principles ◽  
Solder Joints ◽  
Electron Backscatter Diffraction ◽  
First Principles Calculation ◽  
Dissolution Behavior ◽  
Cu Substrate ◽  
Crystallographic Characteristic ◽  
Calculation Results ◽  
Reliability Of Solder Joints ◽  
Characteristic Effect

The crystallographic characteristic effect of Cu substrate on cathode dissolution behavior in line-type Cu/Sn–3.0Ag–0.5Cu (SAC305)/Cu solder joints during electromigration (EM) was investigated by scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and first-principles calculations. The SEM and EBSD results show that the crystallographic characteristic of Cu substrate is crucial to cathode dissolution behavior under a direct current of 1.5 × 104 A/cm2 at 125 °C ± 2 °C. When the (001) plane of copper grain adjacent to the Cu3Sn/Cu interface is perpendicular or nearly perpendicular to the current direction, local cathode dissolution tips are easily formed, whereas the (111) plane remains mostly undissolved, which finally leads to the inhomogeneous cathode serrated dissolution in the substrate. The first-principles calculation results reveal that the different surface energies and energy barriers of the different crystallographic planes of Cu grains in the substrate are responsible for the local cathode dissolution tips. Adjusting the copper grain in a substrate to a crystal plane or direction that is difficult to dissolve during EM is a promising method for improving the reliability of solder joints in the future.

FIRST PRINCIPLES CALCULATION OF THE PHONON SPECTRA OF SOLIDS

1981 ◽  
Vol 42 (C6) ◽  
pp. C6-625-C6-627 ◽  
Author(s):  
P. E. Van Camp ◽  
V. E. Van Doren ◽  
J. T. Devreese
Keyword(s):  
First Principles ◽  
First Principles Calculation ◽  
Phonon Spectra
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