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The surface behaviors of boron (B), phosphorus (P) atom, and B/P_C dimer on the reconstruction diamond (001) surface was discussed. The adsorption and diffusion energies of B, P atom, and B_C, P_C dimer on the reconstruction surface based on diamond surface were calculated by first-principle method based on density functional theory. The stable adsorption site of B and P was the bridge–dimer chain of the ring closing of diamond surface with highest adsorption energy. The bond breaking during migration of the B atom with the active energy was more difficult than that of the phosphorus atom. The two kinds of evolution pathways of B_C or P_C dimer from ring closing to ring opening were according to the atom diffusion order with the same initial and final configurations. A high active energy makes it difficult for the B atom to move out of ring closing than the C atom of B_C dimer diffusion. However, the C atom leads to the diffusion of P_C dimer out of ring closing with lower active energy. To reduce the active energy, the P atom chooses the circuitous diffusion pathway. The active atoms improved the B/P_C dimer diffusion between the ring closing and ring opening. [ABSTRACT FROM AUTHOR]

The adsorption and migration activation energies of a silicon (Si) atom on a hydrogen-terminated diamond (001) surface were calculated using first principles methods based on density functional theory. On the fully hydrogen-terminated surface, the surface carbon atoms possess saturated bonds. The Si atom cannot bond with the surface carbon atoms; thus, the adsorption energy of the Si atom is low. However, on the hydrogen-terminated surface with one or two open radical sites (ORS), the adsorption energy of a Si atom increases to 3.1 eV and even up to 4.7 eV, thereby forming a stable configuration. Along the three ORS in the direction of dimer row or chain, a Si atom can migrate between two deep basins with migration activation energies at 1.5 or 1.3 eV. Given the relatively large energy barrier at approximately 3.8 or 4.7 eV, escaping from the deep basin is difficult for the Si atom. This investigation showed that the number and distribution of ORS, namely, the adsorption site of hydrogen atoms and the removal site of surface hydrogen atoms, can affect the adsorption and migration of Si atoms on the hydrogen-terminated diamond surface. Electron structure analysis further reveals that the reactivity of the surface C atoms and the charge transfer amount between the Si and surface C atoms affect the adsorption and migration of Si atoms. [ABSTRACT FROM AUTHOR]

To apply the high hardness of TiN film to soft and hard multilayer composite sheets, we constructed a new type of composite structural material with ultra-high strength. The strain of crystal and cohesive energy between the atoms in the eight structures of N atom, Ti atom, 2N2Ti island and TiN rock salt deposited on the Al(001) surface were calculated with the first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory. The calculations of the cohesive energy showed that N atoms could be deposited in the face-centered-cubic vacancy position of the Al(001) surface and results in a cubic structure AlN surface. The TiN film could be deposited on the interface of -AlN. The calculations of the strains showed that the strain in the TiN film deposited on the Al(001) surface was less than that in the 2N2Ti island deposited on the Al(001) surface. The diffusion behavior of interface atom N was investigated by a nudged elastic band method. Diffusion energy calculation showed that the N atom hardly diffused to the substrate Al layer. [ABSTRACT FROM AUTHOR]

Adsorption and migration behaviours of Nb–C atoms on a clean diamond (0 0 1) surface were investigated using first principles methods based on density functional theory to develop a new kind of diamond composition film. Firstly, the adsorption and minimum migration energies of a single Nb atom on a surface were calculated to obtain the migration activation energy. Configuration evolutions of two atoms of 1Nb1C and three atoms of 2C1Nb were then studied to determine the effect of the Nb addition. Migrations of a single Nb atom on the clean diamond (0 0 1) surface along a dimer row and along a dimer chain were found to have energy barriers of 2.008 and 2.099 eV, respectively. The barrier was smaller than the barrier of a single carbon atom migrating along a dimer chain. Thus, the migration of the Nb atom is easier than that of the carbon atom. Besides, comparison of the configuration evolution activation energy of 2C1Nb three atoms with that of 2C dimer showed the effect of adding Nb on promoting 2C dimer migration. [ABSTRACT FROM AUTHOR]

The adsorption and migration energies of a single carbon atom and the configuration evolution energies of two carbon atoms on a clean diamond (0 0 1) surface were calculated using the first principle method based on density functional theory to investigate the formation of ultra-nanocrystalline diamond (UNCD) film. The activation energy of a single atom diffusing along a dimer row is 1.96 eV, which is almost the same as that of a CH 2 migrating along a dimer row under hydrogen-rich conditions. However, the activation energy of a single atom diffusing along a dimer chain is 2.66 eV, which is approximately 1.55 times greater than that of a CH 2 migrating along a dimer chain in a hydrogen-rich environment. The configuration evolution of the two carbon atoms is almost impossible at common diamond film deposition temperatures (700–900 °C) because the activation energies reach 4.46 or 5.90 eV. Therefore, the high-energy barrier could result in insufficient migration of adatoms, leading to the formation of amorphous in UNCD films in hydrogen-poor CVD environment. [ABSTRACT FROM AUTHOR]

To develop a new type of diamond composite film, the adsorption energies and minimum migration energies of a single yttrium atom on a diamond (001) surface were calculated with the first principle method based on density functional theory (DFT). Moreover, the total energies of some 1C1Y and 2C1Y configurations and their evolution energies were calculated to study the effect of yttrium additions. The investigation results showed that (1) the migration activation energies of a single yttrium atom along a dimer row and a dimer chain were 0.3505 eV and 1.0128 eV, respectively, indicating that migration of an yttrium atom on a diamond (001) surface is relatively easy; and (2) the migration activation energies of the carbon atoms in configurations of 2C1Y three atoms were obviously reduced, manifesting that the yttrium addition has promotion effects on migration of the carbon atoms on a clean diamond (001) surface. [ABSTRACT FROM AUTHOR]

A novel type of diamond/Si nano-composite thin films is proposed to improve the performance and quality of nano-diamond films. The function of Si atoms in the formation was explored by analysing the evolution of C and Si atoms in diamond/Si nano-composite films. The adsorption, migration, and evolution of the C–Si island configurations on the diamond (0 0 1) surface was studied by using first-principle method based on the density functional theory (DFT). The results indicate that the maximum adsorption energy of the C and Si atoms on the diamond (0 0 1) surface are 4.96 and 4.39 eV, respectively, which implies Si atoms tend to diffuse out of the diamond crystal and formed C–Si interface on the grain boundary. In the same migration pathway, the migration activation energy of the Si particle was 0.865 eV, and the C particle was 1.957 eV. Therefore, the Si atoms migrated easily onto diamond (0 0 1) surface. In the 3C–1C-1 configuration, the C atoms outside the 3C island migrated into the island to form a 4C island in the diamond structure. However, in the 3C–1C-2 configuration, the C atoms outside the 3C island did not migrate into the 3C island, which destroyed the diamond surface. In the 3C–1Si-1 and 3C–1Si-2 configurations, Si atoms migrated into the 3C island to form the 3C1Si island. The Si atoms stabilized the structure of the diamond and eliminated non-diamond carbon atoms, hydrogen atoms and defects in the nano-diamond films. [ABSTRACT FROM AUTHOR]

The adsorption energy of the 4C1Si island configurations and the diffusion activation energies of carbon and silicon atoms on diamond (0 0 1) surface were calculated with first principle method based on density functional theory (DFT) to study the growth of diamond films and the growth position of silicon particles after they are mixed into the composite film. The 4C1Si island configurations consist of five types of C-by-3C1Si configurations and four types of Si-by-4C configurations. The adsorption energy and total energy of the 4C1Si island configurations were calculated firstly. In addition, the diffusion activation energies of the carbon and silicon atoms were calculated. The results show that: (1) the adsorption energy of the Si-by-4C island configurations is higher than that of the C-by-3C1Si island configurations. This indicates that it is not easy for silicon atoms to remain stable in the 3C1Si island. In contrast, silicon atoms are easy to move out of the island so that the carbon atoms out of the 3C1Si Island can enter the island to form the 4C island; (2) Compared with the carbon atom, silicon atom needs lower diffusion activation energy to move into or out of the island. This shows that silicon atoms are more active than carbon atoms. Thus, it is easier for silicon particles to fill the vacancy defects in diamond/Si films, improving the compactness of the diamond composite films. [ABSTRACT FROM AUTHOR]

In order to improve the quality of nano-diamond films, a new type of diamond/Si nano-composite films was proposed. The monolayer Si interface and monolayer SiC interface were studied in this paper. The system total energies and adsorption energies of monolayer Si and monolayer SiC on diamond (001) surface were calculated with first principle method based on the density functional theory (DFT) to investigate the stability of the two kinds of interface structures in the Diamond/Si nano-composite films. Moreover, the variation of the configuration energy and structures when the hydrogen atom and CH 2 radical adsorbed on the two kinds of interfaces were researched to verify whether the diamond phase was able to nucleate and grow or not in the process of diamond/Si nano-composite films deposition. It turned out that (1) the diamond surface structure which is terminated by monolayer silicon atoms is not very stable. It is difficult to form the stable monolayer Si interface in diamond/Si nano-composite films; (2) the monolayer SiC interface with the carbon and silicon atomic ratio of 1:1in which the carbon and silicon atoms are located in the same row respectively is a more stable structure. The interface is conductive to the second nucleation in the process of diamond growth. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigate the behaviors of Nb, Si, N atom on NbN(001) and (111) surfaces. [•] The adsorption and diffusion of single atom on NbN(001) and (111) were calculated by DFT. [•] The potential energy surface of single atom on NbN(001) and (111) surfaces were investigated. [•] The diffusion process of single on NbN(001) and (111) were calculated by nudged elastic band. [Copyright &y& Elsevier]

The transition metal‐related centers of diamond exhibit good properties. Herein, a first‐principles method based on density functional theory (DFT) is used to study single‐doped Ti‐related point defect structures and codoped structures of Ti and B or N, which possibly exist in diamond; the electronic structure and formation energy are also calculated. The results from structural calculations show that Ti is more likely to be located adjacent to a vacancy to form a TiV structure, which is more stable than other configurations. Ti doping introduces impurity levels into the pure diamond band gap, and the possible energy level transitions are determined. The results from the calculations of the codoped system show that the incorporation of N or B atoms is beneficial for the formation of defect structures and that the incorporation of N optimizes the energy band structure of the defects. When a substitutional Ti atom is located adjacent to a B atom and forms a Ti–B structure, and when four N atoms replace the corresponding neighboring C atoms around TiV to form a TiV–4N structure (which is similar to the NE8 configuration), the structure shows a better energy band structure, which presents new color centers. [ABSTRACT FROM AUTHOR]

The elastic properties and electronic structure of the solid solution of CeO 2 –M (M = Ti, Zr, Hf, V, Nb, Ta) are studied using first principle methods based on density functional theory (DFT). The investigation shows that the elastic constants ( B , G , E , C 11 and C 12 ) of the solid solution structure of the CeO 2 –M system have increased, resulting in improved mechanical properties, particularly for CeO 2 –Zr. The elastic constant C 44 in CeO 2 –Ti and CeO 2 –V shows a marked reduction. The elastic modulus of CeO 2 –Nb significantly increased, and its anisotropy is not significantly different from CeO 2 . By calculating the energy band and density of states, it is shown that CeO 2 is an insulator, and there are two band gaps. For transition metal solid solutions, the lattice constant of the CeO 2 –M system decreases, and the second band gap disappears because the Ce atomic contribution reduces, and there is overlap of the 4f and 5d orbital energies. The valence and conduction bands of the CeO 2 –M system (Ti, Zr, Hf) were found to shift slightly, with the band gaps reducing to 2.03 eV, 2.477 eV, and 2.44 eV respectively. The band structure of the CeO 2 –M system (V, Nb, Ta) as a whole moves down, and the second band gap disappears. For bands near the Fermi level, the band gaps are 1.37 eV, 2.51 eV, and 2.73 eV respectively. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effects of Si doping in CeO 2 (111) surface on the polishing performance. For this purpose, the structure and electronic properties of pure CeO 2 (111) surface and Si-doped surface were calculated and compared by the first principles based on density functional theory. The reduction capabilities of the two surface systems were analyzed. Calculated results demonstrate that the ionic structure of Si-doped surface presents a symmetric change and that the formation energy of surface O vacancy decreases by 1.388 eV, indicating that Si doping is conducive for the reduction in surface system. Two electrons left by the O vacancy in the reduction system are obtained by the nearest 2 Ce 4+ , and the Ce 4+ are reduced to Ce 3+ . After Si doping, the hybridization state between Si ion and adjacent Ce and O ions occurs at the Fermi level. Therefore, the synergistic effect of Si doping and O vacancy can enhance the reactivity of CeO 2 polishing particle surface. [ABSTRACT FROM AUTHOR]

Structures of transition metal nitrides (TMNs) are optimized using the plane-wave pseudopotential method based on density functional theory. Energy as a function of volume curves are calculated to predict the phase transition pressures. Density of states (DOS), charge density difference, and charge transfers are calculated. The elastic constant (C 11 ) and modulus (G) as a function of pressure are computed. Results show that TMNs in the WC structure is most stable at normal pressure. All TMNs exhibit metallic, covalent and ionic property. Metallic character increase and covalent property reduce with increasing atomic number of TM atom. The elastic constant (C 11 ) and modulus (G) increase linearly with increasing pressure due to stronger hybridization, bonding and covalent property. Thus, mechanical property enhance under external pressure. [ABSTRACT FROM AUTHOR]

The separation and aggregation of Si atoms around TaN grains during deposition of Ta–Si–N nanocomposite films were studied, and the adsorption energies, charge transfer and atomic partial density of state of Si–2N2Ta islands on the TaN (001) surface and diffusion energy of the islands during their evolution were evaluated using the first-principles method based on density functional theory (DFT). In the lowest total energy stable configuration, N and Ta atoms tended to combine to form 2N2Ta islands, whereas Si atoms tended to stay at a position diagonal to the Ta atom outside of the island. Si atoms entered the position of the missing N atom of the TaN island and formed a substitute solid solution during Ta–Si–N growth. The Si atoms of the solid solution in the island could be easily extruded by Ta- or N-rich island during the deposition process. The process of Si atom extrusion by a N atom which was the configuration of N–by–2Ta1N1Si island evolved into Si–by–2N2Ta island in rich N-atom. The process of Si atom was extruded by the Ta atom which was the configuration of Ta–by–2N1Ta1Si island evolved into Si–of–2Ta2N island, that reduced the total energy of island. The diffusion energies of these evolutions were 0.974 and 1.712 eV, respectively. The Si atoms and TaN grain phase tended to separate during the deposition process. Si atoms could give way to Ta and N atoms during the Ta–Si–N nanocomposite film deposition process. [ABSTRACT FROM AUTHOR]