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Using first-principles calculations, we performed systematic investigation on the electronic and mechanical properties of sodium chlorides with different stoichiometries at high pressures. It was found that most of the phases are metallic except the Pnma-NaCl 3 with a gap of 2.155 eV. The extended Cl (or Na) sublattice at Cl-rich (or Na-rich) conditions contributes to the metallization. Accompanied by metallization, the Na m Cl n crystals exhibit good ductility in contrast to the brittle NaCl crystal, due to the changes of binding features induced by high pressure. These results are expected to be useful for understanding the exotic properties of NaCl at high pressures.

Using first-principles calculations, we study the structural, mechanical and electronic properties of the layered silica nanostructures built on base of silica bilayers consisting of four- and six-membered Si–O ring (4 MR and 6 MR) units. These silica nanostructures have high stability and good flexibility comparable to graphene and can serve as a promising precursor for the fabrication of well-ordered silica nanotubes. The porous structure and wide band gap of the silica nanomaterials may find applications in gas separation, slow-release microcapsules, and catalyst supports.

Using first-principles calculations, we predicted hexagonal boron nitride (h-BN) with flat surface is an ideal substrate for silicene. Van der Waals interactions hold silicene and h-BN together, forming silicene/BN moire superstructures. The moire superstructures open a band gap of about 30 meV at the Dirac point of silicene at equilibrium distance. The band gap is almost independent of the rotation angle between the two lattices, but can be effectively tuned by changing the interlayer spacing. The high Fermi velocity of silicene is well preserved in these superstructures. These features are helpful in achieving applications of silicene in nanoscale electronic devices.

Boron-nitride (BN) domains in graphene or graphene domains in BN monolayer offer additional freedoms for tuning the electronic properties of these BN/C nanostructures, which is quite crucial for the applications in nanoscale devices. Based on first-principles calculations combined with a simple Hubbard model, we show that the electron zero-energy states (ZESs) of BN/graphene core–shell quantum dots (QDs) in triangular shapes can be well tuned by varying the size and topology of each domain. The net spin of the systems is dominated by the graphene segment which can be described by a Liebʼs theorem. We also demonstrated that a π -electron Hubbard model within a mean-field approximation is implementable in dealing with the electron spin-polarization of BN/C hetero-structured graphene-like materials. This provides an efficient theoretical approach for the BN/C systems where electron spin-polarization is involved.

We performed first-principles calculations to investigate the electronic structures and magnetic properties of neutral and charged intrinsic defects of wurtzite ZnO. Our results show that an isolated single charged Zn vacancy can introduce a magnetic moment of 1.00 μ B , and may be responsible for the unexpected ferromagnetism in the system.

We performed first-principles calculations to study the energetics, IR spectra, and electronic structures of silica nanorings (NR) consisting of two- and four-membered ring (2-4MR) units. A comparison study of other silica clusters, such as nanochains (NC) and nanorings formed by two-membered rings (2MRs) was made. The results show that for small-size (SiO2)n clusters with n 24 , the nanochains composed of 2-4MRs (2-4MR-NCs) are more stable than other kinds of NRs and NCs. When n > 24 the 2-4MR-NRs structures become energetically favorable. 2-4MR-NRs have the narrowest HOMO–LUMO gaps which increase with increasing cluster size, distinctive IR spectra characterized by several peaks at the 1000–1150 cm−1 region.

Optical emission of the plasma generated on SiC samples by pulsed laser beam from an Nd:YAG laser was used to investigate the spatial evolution of the electron temperature ( T e ) and density ( N e ) of the plasma. The range and the profile of the plasma were characterized by the electron temperature T e and the electron density N e , as functions of the distance from the SiC surface. It was found that the characterized spatial distribution closely coincided with the spatial images of the plasma recorded by a digital camera. The results obtained from the two different experimental measurements are consistent with other data from the literature, obtained either by models or experiments. The present result may give the insight to the complex physical phenomena in the thin film preparations using the pulsed laser deposition (PLD).

The energetics, stable configurations and electronic structures of the ( ZnO ) n clusters for n ranging from 9 to 64 have been studied by using first-principles calculations. The formation energy of the bubble-like (b-)clusters decreases with the increase of cluster size n, and exhibits an approximately linear relationship to 1 / n for n > 16 . The b-clusters are energetically more favorable than the wurzite-derived (w-)clusters for n 26 , but become less stable than the w-clusters for n ⩾ 26 . The HOMO-LUMO gap of the w-clusters is narrower than that of the b-clusters.

We performed ab initio calculations on the cytosine-functionalized silicon-doped single walled carbon nanotubes (SWNT). The results show that silicon substitutional doping to SWNT can dramatically change the atomic and electronic structures of the SWNT. And more importantly, it may provide an efficient pathway for further sidewall functionalization to synthesize more complicated SWNT based complex materials, for example, our previously proposed base-functionalized SWNTs, because the doping silicon atom can improve the reaction activity of the tube at the doping site due to its preference to form sp3 hybridization bonding.

We have investigated the electronic structures of C-doped (9,0) boron nitride nanotubes (BNNTs) and hydrogen-decorated C-doped (9,0) BNNTs using density functional theory (DFT). It is found that the doping effect of C-doped BNNTs can be compensated by adsorption of H atom on the C sites. The adsorption energies for hydrogen atoms on different adsorption sites on BNNTs and C-doped BNNTs are obtained by using ONIOM method. The results indicate that the most favorable configuration of the adsorption structures is a hydrogen atom adsorbed on the C site of C-doped BNNT.

We carry out first-principles calculations to explore the potential energy profiles of Li confined inside single-walled carbon nanotubes (SWNTs) and the subsequent condensation processes. We found that Li has high mobility around tube axis with the energy barrier less than 47 meV, whereas the diffusion barrier along radial direction is as higher as 380 meV. This characterizes the condensation of Li atoms when placed randomly into SWNTs, resulting in nanowires with single or multi-shelled morphologies depending on the diameter of SWNTs. The charge transfer from Li nanowires to SWNTs is significant, indicating stronger couplings between them.

Molecular dynamics simulations (MDSs) are used to study the collisions of deuterium (D) and tritium (T) atoms with single-wall carbon nanotube (SWNT) in the incident energy range of 1–33 eV. The MDSs show the scattering, encapsulation of deuterium and tritium, and the formation of exohedral D-SWNT, T-SWNT complexes. The hole on the sidewall induced by energetic atoms can be healed in several picoseconds by annealing at room temperature.

Range distributions for fluorine ions in 19 F + -implanted potassium tantalite niobate (KTN) in an energy range of 80–350 keV were measured by using the 19 F (p,αγ) 16 O resonant nuclear reaction at E R =872.1 keV, with width Γ =4.2 keV. A proper convolution calculation method was used to extract the true distributions of fluorine from the experimental excitation yield curves. The experimental range distribution parameters, R p and ΔR p , were compared with those obtained from Monte Carlo simulation codes. The electronic stopping powers for F + ion in KTN were derived through fitting the projected range distributions simulated by using TRIM/XLL code to the experimentally measured range distributions. It is shown that the electronic stopping cross sections obtained in this work agree well with those calculated by using TRIM90 and can be well described by the four-parameter formulae. But they are systematically larger than the results obtained from TRIM98 code.