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Previously, we reported that the - (Mn--O-) orbital hybridization induces Mn valence change (MnMn) in the octahedron. The electron transfer mechanism can be controlled by modifying the Mn- orbital in the octahedron. Here, we used the density functional theory (DFT) with generalized gradient approximation (GGA) and two-dimensional correlation analysis (2D-CA) techniques to calculate the electron transfer mechanism of the V (Nb or Ta) substituted NiMn2O4 (NMO) in the temperature range of 50-1500 K. The results show that the heat accumulation accelerates the O- orbital splitting, inducing charge disproportionation. The V- substituted Mn increases the intensity and of the partial density of state (PDOS) at conduction band (1-3 eV), this enhances the V--O- - orbital. The Nb-/Ta- substituted Mn reduces the intensity of the PDOS at conduction band (1-5 eV), this weakens the Nb-/Ta--O- - orbital. This study effectively analyzes the microscopic changes of the electron transfer caused by the heat accumulation, provides a theoretical basis for the design of NMO-based negative temperature coefficient (NTC) thermistors. [ABSTRACT FROM AUTHOR]

Understanding how plutonium (Pu) doping affects the crystalline zircon structure is very important for risk management. However, so far, there have been only a very limited number of reports of the quantitative simulation of the effects of the Pu charge and concentration on the phase transition. In this study, we used density functional theory (DFT), virtual crystal approximation (VCA), and two-dimensional correlation analysis (2D-CA) techniques to calculate the origins of the structural and electronic transitions of Zr 1− c Pu c SiO 4 over a wide range of Pu doping concentrations ( c = 0–10 mol%). The calculations indicated that the low-angular-momentum Pu-f xy -shell electron excites an inner-shell O-2s 2 orbital to create an oxygen defect (V O-s ) below c = 2.8 mol%. This oxygen defect then captures a low-angular-momentum Zr-5p 6 5s 2 electron to form an sp hybrid orbital, which exhibits a stable phase structure. When c > 2.8 mol%, each accumulated V O-p defect captures a high-angular-momentum Zr-4d z electron and two Si-p z electrons to create delocalized Si 4+ → Si 2+ charge disproportionation. Therefore, we suggest that the optimal amount of Pu cannot exceed 7.5 mol% because of the formation of a mixture of ZrO 8 polyhedral and SiO 4 tetrahedral phases with the orientation (10-1). This study offers new perspective on the development of highly stable zircon-based solid solution materials. [ABSTRACT FROM AUTHOR]

Here, we present a simulation research of the heterogeneous oxidation mechanism of SO 2 on Al 2 O 3 (mineral oxides) surface by H 2 O 2 , density functional theory (DFT) calculations was used to investigate the adsorption mechanism of SO 2 and H 2 O 2 on the perfect and O defect γ-Al 2 O 3 (110) surfaces. The results show that SO 2 molecularly adsorbed on the prefect and O defect surfaces, while H 2 O 2 was adsorbed in the molecule form on the perfect surface. In particular, H 2 O 2 dissociation only occurred on the O defect γ-Al 2 O 3 (110) surface. The oxygen defects not only enhanced the adsorption intensities of H 2 O 2 and SO 2 , but also promoted the H 2 O 2 decomposition (H 2 O 2 →OH + OH). Analysis of partial density of states, differential charge density and Mulliken population indicated that H 2 O 2 decomposition followed the Haber-Weiss mechanism (formation of surface OH), and SO 2 was oxidized by the OH radicals to form HOSO 2 molecule when SO 2 and H 2 O 2 co-adsorbed on O defect γ-Al 2 O 3 (110) surface. Moreover, the lower energy barrier of H 2 O 2 decomposition (32.69 kJ/mol) and SO 2 oxidation (78.21 kJ/mol) demonstrated that SO 2 to be oxidized easily by the H 2 O 2 on the O defect γ-Al 2 O 3 (110) surfaces. These results can well explain the formation mechanism of OH radicals and the oxidation mechanism of SO 2 by H 2 O 2 on the mineral dust at the molecular level, which is of great significance for understanding the role of H 2 O 2 in the heterogeneous oxidation of SO 2 on the mineral dust and the formation mechanism of sulfate aerosols in the atmosphere. [ABSTRACT FROM AUTHOR]

Here, we present a simulation study of temperature‐dependent electronic transitions in BiVO3 (BVO) and BiNbO3 (BNO) using density functional theory (DFT) together with generalized gradient approximation (GGA) and two‐dimensional correlation analysis (2D‐CA). The results indicate that heat accumulation can accelerate the degeneracy of V‐3d orbital in BVO and the splitting of Nb‐4d orbital in BNO at 750 K. We found changes in the type of d–p hybrid orbital as follows, for BVO: V‐dx2+y2 + dZ2‐O‐2pz → V‐dx2+y2‐O‐2pz; and for BNO: Nb‐dx2+y2‐O‐2pz → Nb‐dx2+y2 + dZ2‐O‐2pz. Furthermore, we found changes in the type of hybrid orbital leading to the following electron–electron interactions, for BVO: t2g (V‐dZ2‐O‐2pz) + eg (V‐dx2+y2‐O‐2pz) → t2g (V‐dx2+y2‐O‐2pz); and for BNO: t2g + eg (Nb‐dx2+y2 + dZ2‐O‐2pz) → t2g (Nb‐dx2+y2‐O‐2pz) + eg (Nb‐dz2‐O‐2pz). The electronic transitions are determined by a charge‐transfer from the occupied O‐2p4 orbitals to the unoccupied V‐3d3 (or Nb‐4d3) and Bi‐6p3 orbitals. Due to the temperature‐dependent electronic structure closely related to these electronic transitions, this study provides a new perspective for the design and improvement of BFO‐based temperature‐sensitive devices. [ABSTRACT FROM AUTHOR]

Here, we present a simulation study of temperature‐dependent electronic transitions in BiVO3 (BVO) and BiNbO3 (BNO) using density functional theory (DFT) together with generalized gradient approximation (GGA) and two‐dimensional correlation analysis (2D‐CA). The results indicate that heat accumulation can accelerate the degeneracy of V‐3d orbital in BVO and the splitting of Nb‐4d orbital in BNO at 750 K. We found changes in the type of d–p hybrid orbital as follows, for BVO: V‐dx2+y2 + dZ2‐O‐2pz → V‐dx2+y2‐O‐2pz; and for BNO: Nb‐dx2+y2‐O‐2pz → Nb‐dx2+y2 + dZ2‐O‐2pz. Furthermore, we found changes in the type of hybrid orbital leading to the following electron–electron interactions, for BVO: t2g (V‐dZ2‐O‐2pz) + eg (V‐dx2+y2‐O‐2pz) → t2g (V‐dx2+y2‐O‐2pz); and for BNO: t2g + eg (Nb‐dx2+y2 + dZ2‐O‐2pz) → t2g (Nb‐dx2+y2‐O‐2pz) + eg (Nb‐dz2‐O‐2pz). The electronic transitions are determined by a charge‐transfer from the occupied O‐2p4 orbitals to the unoccupied V‐3d3 (or Nb‐4d3) and Bi‐6p3 orbitals. Due to the temperature‐dependent electronic structure closely related to these electronic transitions, this study provides a new perspective for the design and improvement of BFO‐based temperature‐sensitive devices. [ABSTRACT FROM AUTHOR]

We explored the effect of contact time on the interfacial interaction mechanism of amino acids (AAs) connected to the aluminol group (AlOH) and interlayer Ca ions of Ca-montmorillonite (Ca Mt) in an aqueous solution using density functional theory (DFT) and two-dimensional correlation analysis (2D-CA) technology. The results showed that these interactions include electrostatic (or van-der-Waals) interaction, cation exchange and hydrophilic interaction. In particular, the electrostatic (or van-der-Waals) interaction between the –COO−(H) (and –NH 3 +) groups of the AAs and surface negative O atoms of Ca Mt were found to be the main interaction leading to the adsorption behaviour of AAs onto Ca Mt. With increasing contact time, the Ca-d0 orbital splitting (d x 2 +y 2 → d x 2 +y 2 + d Z 2) not only changes the orbital coupling between the Ca-d0 and O-2p4 orbitals (Ca-d x 2 +y 2-O-2p4 → Ca-d x 2 +y 2 + d Z 2-O-2p4) but also enhances the formation of Ca+–COO−(H) p-p σ (neutral: glycine and serine) and Ca+-NH 3 + p-p π (charged: glutamate and arginine) hybrid orbitals, as well as the cation exchange (AlOH-Ca + AAs) that mainly contributes to the short-range van-der-Waals interaction. Furthermore, the H-1 s (H 2 O) orbital is degenerate, which in turn enhances the orbital overlap of H-1 s (H 2 O) with O-2p4 (-HOCO) and N-2p3 (-NH 3), leading to the formation of hydrated clusters: -NH 3 ·(H 2 O)+ and –HOCO·(H 2 O)−. The hydrophilic interaction (AlOH-H 2 O + AAs) mainly contributes to the long-range electrostatic interaction. The results of the study provide a new perspective to understand the adsorption process of AAs onto clay mineral surfaces. Unlabelled Image • Calculation of the interface interaction between various AAs and Ca-Mt in the water environment. • Orbital hybridization and electronic transition mechanism between AAs and Ca/H 2 O was explained in the interface. • The transition mechanism of van-der Waals (Ca + AAs) and electrostatic interactions (H 2 O + AAs) with contact time. [ABSTRACT FROM AUTHOR]

Previously, we reported that the - (Mn--O-) orbital hybridization induces Mn valence change (MnMn) in the octahedron. The electron transfer mechanism can be controlled by modifying the Mn- orbital in the octahedron. Here, we used the density functional theory (DFT) with generalized gradient approximation (GGA) and two-dimensional correlation analysis (2D-CA) techniques to calculate the electron transfer mechanism of the V (Nb or Ta) substituted NiMn2O4 (NMO) in the temperature range of 50-1500 K. The results show that the heat accumulation accelerates the O- orbital splitting, inducing charge disproportionation. The V- substituted Mn increases the intensity and of the partial density of state (PDOS) at conduction band (1-3 eV), this enhances the V--O- - orbital. The Nb-/Ta- substituted Mn reduces the intensity of the PDOS at conduction band (1-5 eV), this weakens the Nb-/Ta--O- - orbital. This study effectively analyzes the microscopic changes of the electron transfer caused by the heat accumulation, provides a theoretical basis for the design of NMO-based negative temperature coefficient (NTC) thermistors. [ABSTRACT FROM AUTHOR]

We elucidated a number of facets regarding arginine–glycine–aspartate (RGD)–bismuth ferrite (BFO)-(1 1 1) membrane interactions and reactivity that have previously remained unexplored on a molecular level. Results demonstrate the intra-molecular interaction facilitates a “horseshoe” structure of RGD adsorbed onto the BFO-(1 1 1) membrane, through the electrostatic (Asp-cation-Fe) and water-bridge (O H 2 O and H 2 O NH 2 ) interactions. The effect of structural and electron-transfer interactions is attributed to the cation-valences, indicating that the divalent cations are electron-acceptors and the monovalent cations as electron-donors. Notably, the strongly bound Ca 2+ ion exerts a “gluing” effect on the Asp-side-chain, indicating a tightly packed RGD–BFO configuration. Thus, modulating the biological response of BFO-(1 1 1) membrane will allow us to design more appropriate interfaces for implantable diagnostic and therapeutic perovskite-type micro-devices. [ABSTRACT FROM AUTHOR]

Perovskite bismuth ferrite-BFO (111) membranes, as a potential sensitive electrochemical sensor, are investigated for the detection of amino acids by molecular dynamics (MD) and density functional theory (DFT) techniques. For the detection mechanism of the ferromagnetic phase BFO (111) membrane, the cation bridge model indicates that there is a electronic signal amplification (0.01–0.09 V), due to the enhancement of Fe 3+ –COO − triple degeneracy orbit (t 2g ). It is an excellent detection sensitivity for various AAs that can be used to distinguish the surface charges. However, the Fe-d 7/2 momentum changes its orientation from upward to downward, on the anti-ferromagnetic phase BFO (111) membrane. The empty d 0 orbital degenerates to the O↓ orbital that weakens the Fe–O electron transfer rate, weakening the electronic signal (0.005–0.05 V). [ABSTRACT FROM AUTHOR]