UNDERSTANDING INSIGHT OF METHANOL ADSORPTION ON 2 ATOMIC COPPER DEPOSITED OVER ZNO(10¯1 0) SURFACE: A DFT STUDY

In this study, depositing with two copper atoms (2Cu) on ZnOsurface, obtaining 2Cu/ZnO surface model, and its applications then for adsorbed CH3OH were investigated using the density functional theory (DFT). In performances, 2Cu was adsorbed on ZnOsurface to form the model of 2Cu deposited over ZnO (2Cu/ZnO). Further, on 2Cu/ZnO surface model, the resulted analysis as density of state (DOS) and electron density difference (EDD) contour plot pointed out that two atomic Cu were formed by the transferred electrons from Cu to ZnO, leading Cu oxidation to become Cu+ ion, while was modeled 2Cu/ZnOsurface. To investigate CH3OH adsorption, many configurations of adsorbed CH3OH on the surface found, in which the most stable configurations were also identified. This result presented that methanol adsorption on 2Cu/ZnO is more favorable than that on ZnO in our previous works.

Insights on Substitution Preference of Pb Ions in Sulfoaluminate Cement Clinker Phases

The doping behaviors of Pb in sulfoaluminate cement (SAC) clinker phases were systematically studied combined with density functional theoretical simulations and experiments. The results present that, in the three composed minerals of C4A3S, C2S, and C4AF, Pb ions prefer to incorporate into C4A3S by substituting Ca ions. Further analyses from partial density of states, electron density difference, and local distortions show that such doping preference can be attributed to the small distortions as Pb introduced at Ca sites of C4A3S. The results and clear understandings on the doping behaviors of Pb ions may provide valuable information in guiding the synthesis of Pb-bearing SAC clinker, thus should draw broad interests in fields from sustainable production of cement and environmental protection.

Structural inheritance and difference between Ti2AlC, Ti3AlC2 and Ti5Al2C3 under pressure from first principles

The structural inheritance and difference between Ti2AlC, Ti3AlC2 and Ti5Al2C3 under pressure from first principles are studied. The results indicate that the lattice parameter a are almost the same within Ti2AlC, Ti3AlC2 and Ti5Al2C3, and the value of c in Ti5Al2C3 is the sum of Ti2AlC and Ti3AlC2 which is revealed by the covalently bonded chain in the electron density difference: Al–Ti–C–Ti–Al for Ti2AlC, Al–Ti2–C–Ti1–C–Ti2–Al for Ti3AlC2 and Al–Ti3–C2–Ti3–Al–Ti2–C1–Ti1–C1–Ti2–Al for Ti5Al2C3. The calculated axial compressibilities, volumetric shrinkage, elastic constant [Formula: see text], [Formula: see text] ratio, bulk modulus, shear modulus, and Young’s modulus of Ti5Al2C3 are within the range of the end members (Ti2AlC and Ti3AlC2) in a wide pressure range of 0–100 GPa. Only Ti2AlC is isotropic crystal at about 50 GPa within the Ti–Al–C compounds. All of the Ti 3d density of states curves of the three compounds move from lower energy to higher energy level with pressure increasing. The similarities of respective bond length, bond overlap population (Ti–C, Ti–Al and Ti–Ti), atom Mulliken charges under pressure as well as the electron density difference for the three compounds are discovered. Among the Ti–Al–C ternary compounds, Ti–Ti bond behaves least compressibility, whereas the Ti–Al bond is softer than that of Ti–C bonds, which can also been confirmed by the density of states and electron density difference. Bond overlap populations of Ti–Ti, Ti–C and Ti–Al indicate that the ionicity interaction becomes more and more stronger in the three structures as the pressure increasing. Mulliken charges of Ti1, Ti2, Ti3, C and Al are 0.65, 0.42, 0.39, −0.73, −0.04 at 0 GPa, respectively, which are consistent with the Pauling scale.

STUDY ON THE RELATIONSHIP BETWEEN VALENCE ELECTRON STRUCTURE AND COATING ORIENTED GROWTH

The coating oriented growth has attracted great attention because of its effect on coating properties. In this paper, the valence electron structures of TiN and Ni were calculated with the empirical electron theory (EET) in solid and molecules for investigating preferred orientation of nitride coatings containing Ni . The calculation results show that Ni (111), CrN (100) and TiN (100) are the maximum crystal-face electron density, respectively. In CrN (or TiN ) coatings, if Ni does not form a single nickel phase, CrN (100) (or TiN (100)) preferred orientation appears easily due to its high crystal-face electron density. When Ni exists as a single phase, CrN (100)/ Ni (111) (or TiN (100)/ Ni (111)) with the minimum crystal-face electron density difference is the most likely to appear in the coatings. Furthermore, high crystal-face electron density difference usually implies fine grain microstructure. The calculation results are consistent with the experimental results.

The Performance Research of Different Concentrations of Methyl Adsorption on Si (110) Surface

First-principles method was carried out to investigate the methyl chemical adsorbing on Si (110) surface. To clarify the different concentrations of methyl on Si (110) surface, the mono-methyl, double-methyl, treble-methyl, and quadruple-methyl on the Si surface adsorption models were comparably investigated. Adsorption energy and methyl C-H bond structure change, density of states and electron density difference were used to analyze the structure change of adsorption models. The adsorption energy shows that Si surface top site has significant sensitivity to methyl, and the adsorption energy increase with the increasing methyl concentrations. The electron density difference data show charge transfer is obvious and electron cloud center tend to Si atom with Si-C bond formed. The PDOS of methyl reveals electron peaks move to the low direction about (5.5036, 5.7868, 5.8572, 5.8788eV) with the increasing concentrations of methyl. The data above exhibit that quadruple-methyl adsorption structure is more stable one. The conclusion can provide the insight for gas detection and sensors.

The Chemisorptions Mechanism Study of Methyl on Different Bonds in Porous Silicon

The absorbing kinetic process of methyl on Si (111) surface was comprehensively studied using the method of quantum mechanics. We optimized the model structures of radical CH3+, Si (111), and CH3+ on Si (111) to obtain a rational convergence for the present calculations. The electron density difference and density of states of each model were calculated by CASTEP. The electron density difference of CH3+ on Si (111) reveals that the charge transfer factor is difference for different absorption positions, which indicates that the bond strength difference. The density of state of model exhibits that the electronic peaks move to the low energy direction. However, the absorption on B (-8.57, -2.19, 0.91) position shows a higher electron shift which evidences that it is the appreciating absorption position.

Analysis of the Effect of Nitrogen on Cold Shortness Behavior of Steel with the Electron Structure Parameters of Phase Interface

Based on the empirical electron theory of solids and molecules (EET), the phase interface electron structure of Fe4N/a-Fe、AlN/γ-Fe、AlN/γ-Fe-C(Al) are calculated, and the reasons that the cold shortness is resulted from nitrogen as well as the add of Al element is helpful to the removal of cold shortness are analyzed with the use of the interface conjunction factors such as,σ and. The calculated results are as follows. The discontinuous electron density difference of phase interface Fe4N/a-Fe under the first order approximation results in the remarkable strengthening effect as well as the significant decrease in toughness and ductility, demonstrating the reason that nitrogen can cause cold shortness; as the electron density difference on AlN/γ-Fe、AlN/γ-Fe-C(Al) phase interface is very large and the continuous number of the phase interface is very small, the add of Al can hinder the growth of grain, as a result, the austenite grain is significantly refined and the removal of cold shortness caused by Fe4N can be achieved.

A STUDY ON STRAIN AFFECTING ELECTRONIC STRUCTURE OF WURTZITE ZnO BY FIRST PRINCIPLES

Density of states and band structure of wurtzite ZnO are calculated by the CASTEP program based on density functional theory and plane-wave pseudopotential method. The calculations are carried out in axial and unaxial strains, respectively. The results of density of states in different strains show that the bottom of the conduction band is always dominated by Zn 4s, and the top of valence band is always dominated by O 2p. The variation of the band gap calculated from band structure is also discussed. In addition, p-d repulsion is used in investigating the variation of the top of the valence band in different strains and the results can be verified by electron density difference.