An Investigation of the Mechanism on Interfacial Charge Transformation of the TiB2/Cu Composites Studied by the First Principles

The charge communications have been widely existed in the metal materials when they are under the processing, the modeling and the failing. We studied the interfacial charge transformation of the TiB2/Cu composites via the first principles method. The layer thickness was predicted by the interfacial charge communications performed on the regions of the TiB2/Cu interfaces. The layer thickness of the Ti-terminated (TT)TiB2/Cu were predicted longer than those of the B-terminated(BT) TiB2/Cu and contrasting with their average vales as 0.75 (nm) and 0.65 (nm), respectively. The Mulliken population was applied to investigate the bond length, bond population and charge transformation of the six TiB2/Cu models. The Ti-Cu bond was only detected in TT-HCP interfaces among the all TT-TiB2/Cu models, which was further confirmed that the metallic bond of the Ti-Cu with the bond length and population as 2.5 Å and 0.22, respectively. Nevertheless, the B-Cu bond were detected in all BT-TiB2/Cu models, and the bond length and population higher than those of B-Cu bond in chemical complexes. The 5 atomic layers were involved in quantitative analyses of the interfacial charge transformation. The results indicate that the charges lost by interfacial Ti atom were inequivalent obtained by Cu and B atoms which nearby the interfacial Ti atoms of the TT-TiB2/Cu. Comparing with the BT-TiB2/Cu models, the charges acquired by the interfacial B atom were most from the Ti and less from the Cu atoms surrounded the interfacial B atoms.

Comparative Hybrid Hartree-Fock-DFT Calculations of WO2-Terminated Cubic WO3 as Well as SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001) Surfaces

We performed, to the best of our knowledge, the world’s first first-principles calculations for the WO2-terminated cubic WO3 (001) surface and analyzed the systematic trends in the WO3, SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001) surface ab initio calculations. According to our first principles calculations, all WO2 or TiO2-terminated WO3, SrTiO3, BaTiO3, PbTiO3 and CaZrO3 (001) surface upper-layer atoms relax inwards towards the crystal bulk, while all second-layer atoms relax upwards. The only two exceptions are outward relaxations of first layer WO2 and TiO2-terminated WO3 and PbTiO3 (001) surface O atoms. The WO2 or TiO2-terminated WO3, SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001) surface-band gaps at the Γ–Γ point are smaller than their respective bulk-band gaps. The Ti–O chemical bond populations in the SrTiO3, BaTiO3, PbTiO3 and CaTiO3 bulk are smaller than those near the TiO2-terminated (001) surfaces. Conversely, the W–O chemical bond population in the WO3 bulk is larger than near the WO2-terminated WO3 (001) surface.

Effects of Vacancy and Hydrogen on the Growth and Morphology of N-Type Phosphorus-Doped Diamond Surfaces

Phosphorus is regarded as the best substitutional donor for n-type diamonds. However, because of vacancy-related complexes, H-related complexes, and other defects in P-doped diamonds, obtaining n-type diamonds with satisfying properties is challenging. In this report, PV and PVH complexes are studied in detail using density function theory (DFT). The formation energy reveals the possibility of emergency of these complexes when doping a single P atom. Although vacancies have difficulty forming on the surface alone, the presence of P atoms benefits the formation of PV and PVH complexes and significantly increases crystal vacancies, especially in (111) diamond surfaces. Compared to (111) surfaces, PV and PVH complexes more easily form on (001) surfaces. However, the formation energies of these complexes on (001) surfaces are higher than those of doping P atoms. Studying the structural deformation demonstrated that both constraints of the upper and lower C layers and forces caused by structural deformation prevented doping P atoms. By analyzing the bond population around these dopants, it finds that the bond populations of P–C bonds of PVH complexes are larger than those of PV complexes, indicating that the PV complexes are not as stable as the PVH complexes.

Ti3O5 and Al2TiO5 Crystals Flotation Characteristics from Ti-bearing Blast Furnace Slag: A Density Functional Theory and Experimental Study

Anosovite crystalline is an ideal mineral for flotation from the Ti-bearing blast furnace (TBBF) slag. Ti3O5 crystal and Al2TiO5 crystal are two kinds of anosovites, and the Al element significantly affects the electronic structure and flotation performance of anosovite. The floatability of Ti3O5 and Al2TiO5 crystals were studied by Mulliken populations, energy bands, and density of states (DOS). In addition, the flotation experiment of the two kinds of anosovite crystals (Ti3O5 and Al2TiO5) was conducted and proved that the density functional theory (DFT) calculation results were accurate. Compared with Ti3O5 crystal, the Fermi energy level of Al2TiO5 crystal shifts around 2 eV in a negative direction by DOS analysis, which is beneficial to flotation. And Al2TiO5 crystal possesses a larger value of bond population, which is 0.41, for Ti-O bonds than Ti3O5 crystal and the bond length of Ti-O in Al2TiO5 crystal is shorter, therefore Al2TiO5 crystal shows a stronger covalency. The changes of the Fermi energy level and the covalency bonds in Al2TiO5 crystal both demonstrated that doping the Al component into the Ti3O5 crystal was beneficial to improve the flotation effect. Moreover, the Al2TiO5 crystal had a higher flotation efficiency compared to the Ti3O5 crystal when the dosages of salicylhydroxamic acid (SHA) and sodium oleate were the same. Therefore, both DFT calculation and experiment show that the flotation effect of the Al2TiO5 crystal is better than that of the Ti3O5 crystal.

Comparative Ab Initio Calculations of ReO3, SrZrO3, BaZrO3, PbZrO3 and CaZrO3 (001) Surfaces

We performed, for first time, ab initio calculations for the ReO2-terminated ReO3 (001) surface and analyzed systematic trends in the ReO3, SrZrO3, BaZrO3, PbZrO3 and CaZrO3 (001) surfaces using first-principles calculations. According to the ab initio calculation results, all ReO3, SrZrO3, BaZrO3, PbZrO3 and CaZrO3 (001) surface upper-layer atoms relax inwards towards the crystal bulk, all second-layer atoms relax upwards and all third-layer atoms, again, relax inwards. The ReO2-terminated ReO3 and ZrO2-terminated SrZrO3, BaZrO3, PbZrO3 and CaZrO3 (001) surface band gaps at the Γ–Γ point are always reduced in comparison to their bulk band gap values. The Zr–O chemical bond populations in the SrZrO3, BaZrO3, PbZrO3 and CaZrO3 perovskite bulk are always smaller than those near the ZrO2-terminated (001) surfaces. In contrast, the Re–O chemical bond population in the ReO3 bulk (0.212e) is larger than that near the ReO2-terminated ReO3 (001) surface (0.170e). Nevertheless, the Re–O chemical bond population between the Re atom located on the ReO2-terminated ReO3 (001) surface upper layer and the O atom located on the ReO2-terminated ReO3 (001) surface second layer (0.262e) is the largest.

The Interfacial Characteristics of Graphene/Al4C3 in Graphene/AlSi10Mg Composites Prepared by Selective Laser Melting: First Principles and Experimental Results

The Al4C3 phase was precipitated via a reaction of graphene (Gr) with Al during selective laser melting (SLM). The interfacial nature of the Gr (0001)/Al4C3 (0001) interface was determined using the first-principle calculation. The simulation results showed that the influence of the stacking site on the interfacial structure was limited and the Al-termination interface presented a more stable structure than the C-termination interface. The Al-termination-CH site interface had the largest work of adhesion (6.28 J/m2) and the smallest interfacial distance (2.02 Å) among the four interfacial structures. Mulliken bond population analysis showed that the bonding of the Al-termination interface was a mixture of covalent and ionic bonds and there was no chemical bonding in the C-termination interface.

Surface Properties and Floatability Comparison of Aegirite and Specularite by Density Functional Theory Study and Experiment

Understanding the differences in surface properties between aegirite and specularite is of great significance to study their separation. In this work, the surface properties of aegirite and specularite, as well as their relationships to floatability, have been explored by first principle calculation, flotation, and Zeta potential measurement. The surface relaxation indicated that the specularite (001) surface appeared to show more surface reconstruction. The unsatisfied bond properties, Mulliken bond population, and surface charge showed that the floatability of specularite was superior to that of aegirite. The flotation results showed that the hydrophobicity of specularite was higher than that of aegirite with dodecylamine (DDA) as the collector. It is infeasible to separate specularite from aegirite by flotation using starch as the depressant, and research of effective reagents with high affinity to the element Si is the subclinical breakthrough point of specularite/aegirite separation.

[Au(CN)2]—Adsorption on a Graphite (0001) Surface: A First Principles Study

Gold is mainly present in the form of [Au(CN)2]− during the cyanide leaching process, and this [Au(CN)2]− can be adsorbed by graphite in carbonaceous gold ore resulting in preg-robbing gold. In order to clarify the adsorption mechanism between the [Au(CN)2]− and graphite, the interaction between the [Au(CN)2]− and graphite (0001) surface was studied using density functional theory (DFT). The distance between [Au(CN)2]− and graphite (0001) decreased from (4.298–4.440 Å) to (3.123–3.343 Å) after optimization, and the shape of [Au(CN)2]− and graphite (0001) obviously changed from straight to curved, which indicated that the [Au(CN)2]− had been adsorbed on the graphite (0001) surface. A partial densities of state (PDOS) analysis revealed that there was little change in the delocalization and locality of the PDOS on the graphite (0001) surface after adsorption. However, the valence bands of the Au 5d orbital, C 2p orbital, and N 2p orbital near the Fermi level moved slightly towards lower energy levels; therefore, the adsorption configuration was stable. An analysis of the Mulliken charge population indicated that the Au, N, and C in [Au(CN)2]− obtained 0.26, 0.18, 0.04 electrons after adsorption, respectively, while C(surf) lost 0.03 electrons. [Au(CN)2]− changed to a conductor from an insulator after adsorption. Taking into account the surface electrical properties of [Au(CN)2]− and graphite (0001), there was still a slight electrostatic adsorption between them. The analysis of adsorption energy, electronic structure, PDOS, electron density, Mulliken charge population, and Mulliken bond population revealed that [Au(CN)2]− could be adsorbed to the graphite (0001) surface; the adsorption was a type of physical adsorption (including electrostatic adsorption) and mainly occurred on the two C≡N. These results contributed to the understanding of the mechanisms involved in preg-robbing gold formation by graphite and the optimization of this process during cyanide leaching.