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Using the Debye shielding model, the effects of plasma shielding on the dielectronic recombination processes of the H-like helium ions are investigated. It is found that plasma shielding causes a remarkable change in the Auger decay rate of the doubly excited 2p 2 3 P 2 state. As a result, the dielectronic recombination cross sections from the doubly excited 2p 2 3 P 2 state increases with the decreasing Debye shielding length.

We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.5 kHz by AFM-based acoustic microscopy The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7kHz to 10kHz, and reached maximum at 8.1kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects.

Based on the reciprocity theorem of the acoustic field, we derive the formula of the reciprocity coefficient of a convergent spherical acoustic wave and we calculate a series of diffraction corrective factor curves of the reciprocity coefficient of transducers. Using these formulae and corrective factors, we calibrate the free field transmitting current response and the free field voltage sensitivity of a focusing transducer using the self-reciprocity method. The experimental results of the reciprocity calibration of the focusing transducer in the frequency range of 2 MHz to 5.4 MHz are presented.

A large aperture transducer with an inner hole has been used to validate the feasibility of using the spheroidal beam equation to solve the acoustic field of the inner holed transducer. The numerical results of several harmonics are presented for the nonlinear field.

Molecular dynamics simulation of MgO crystal at different temperature and pressure was carried out by using the shell model of ionic polarizability. The prediction of thermal expansion is in good agreement with the experiment. The heat capacity has been calculated with a semi-classical approximate method. The calculated values are less than the experimental data because the anharmonic effect and quantum correlation were not taken into account. The changes of transverse-optic and longitudinal-optic modes with the compression ration are also calculated.

The Si–O bond breaking event in the α-quartz at the first triplet (T1) excitation state is studied by using ab initio molecular dynamics (AIMD) and nudged elastic band calculations. A meta-stable non-bridging oxygen hole center and E' center (NBOHC-E') is observed in the AIMD which consists of a broken Si–O bond with a Si–O distance of 2.54 A. By disallowing the re-bonding of the Si and O atoms, another defect configuration (III-Si/V-Si) is obtained and validated to be stable at both ground and excitation states. The NBOHC-E' is found to present on the minimal energy pathway of the initial to III-Si/V-Si transition, showing that the generating of the NBOHC-E' is an important step of the excitation induced structure defect. The energy barriers to produce the NBOHC-E' and III-Si/V-Si defects are calculated to be 1.19 and 1.28 eV, respectively. The electronic structures of the two defects are calculated by the self-consistent GW calculations and the results show a clear electron transition from the bonding orbital to the non-bonding orbital.

Bi1−xTbxFeO3 (x = 0, 0.01, 0.03 and 0.05) nanoparticles are synthesized by the sol-gel method. A single phase perovskite rhombohedral structure of all the samples is established from the Rietveld refined XRD patterns. The substitution of Tb3+ ions to Bi3+ decreases the particle size and enhances the ferromagnetic properties of this system. Interestingly a large maximum magnetization value of 1.73 emu/g at 50kOe can be observed in 1% Tb-doped sample at 300 K. The decrease in band gap may result from the reduced particle size, while the leakage current density also decreases, which is mainly explained by the variation of oxygen vacancies.

We investigate realization of the infinite-dimensional 3-algebras in the classical Calogero—Moser model. In terms of the Lax matrix of the Calogero—Moser model and the Nambu 3-brackets in which the variables are the coordinates qi, and canonically conjugate momenta pi and the coupling parameter β are an extra auxiliary phase-space parameter, we present the realization of the Virasoro—Witt, w∞ and SDiff(T2) 3-algebras, respectively.

The first-principles method of hydrogen adsorption is used to investigate the interaction of H2 with the scandium-porphyrazine (Sc-Pz) and porphyrazine (Pz) clusters. The result shows that the interaction of H2 with Sc-Pz is stronger than with Pz. Then grand canonical Monte Carlo simulations are used to investigate hydrogen adsorption in six designed covalent organic frameworks (COFs), which are designed based on porphyrazine, cyclobutane and scandium. When the pressure is from 0.1 to 100 bar and the temperature is 298 K and 77 K, the hydrogen adsorption capacities of the six COFs are calculated. We further study the importance of Sc and fillers to improve the H2 uptake in the modified COFs by analyzing the isosteric heat of hydrogen adsorption.

Path integral Monte Carlo (PIMC) method is employed to study the thermal properties of the X@C50[X=H2, He, Ne, Ar] system at temperatures from 5K to 300 K. The interaction energies and probability distribution functions of one noble gas atom or H2 inside D5h-symmetry C50 are obtained. A rough sphere model is used in calculating interaction energies, as a comparison. This model gives much lower interaction energy than PIMC calculations on all X@C50, except He@C50. The PIMC method and the sphere model get nearly the same values of interaction energies on He@C50. The spatial distributions are enlarged by the increase in temperature, while the interaction energies change slowly in a wide range of temperature. Temperature is not the major reason for the stability of the system. It is impossible to trap an X atom into C50, except H2 because only the H2@C50 has positive interaction energies from the PIMC calculations.

Using first-principles calculations, we predict that a single C2H4 or C5H5 molecule can form a stable complex with two rare earth metals such as La, Eu, and Ho. The La2C2H4 complex then absorbs up to sixteen hydrogen molecules, reaching a gravimetric storage capacity of 9.5wt% by adding a rare-earth metal atom, The results show that Eu-4f electrons have little impact on the hydrogen adsorption. The nature of bonding between Eu and H2 is due to the hybridization of Eu-5d with the H-1s orbital.

Based on the metal-oxide-semiconductor field effect transistor (MOSFET) stress sensitive phenomenon, a low power MOSFET pressure sensor is proposed. Compared with the traditional piezoresistive pressure sensor, the present pressure sensor displays high performances on sensitivity and power consumption. The sensitivity of the MOSFET sensor is raised by 87%, meanwhile the power consumption is decreased by 20%.

The multi-configuration Dirac—Fock method is employed to calculate the energy levels and transition probabilities for the electric dipole allowed (E1) and forbidden (M1, E2) lines for the 4s24p, 4s4p2 and 4s24d configurations of highly charged Ga-like ions from Z = 68–95. The lifetimes of the 4s24p 2P3/2 level of the ground configuration are also derived. Based on our calculations, it is found that the energy level of the 4s24p 2P3/2 is higher than that of the 4s4p2 4P1/2 for the high-Z Ga-like ions with Z ≥ 74, so as to generate an energy crossing at Z = 74. The effect of the energy crossing is important to the calculation of the 4s24p 2P3/2 level lifetime for Ga-like ions with Z ≥ 74.

The potential energies of H2 molecules with partially truncated and open cage C60 fullerenes, including C58, C55, C54(I), C54(II) and C46, are investigated by means of the density functional theory method. The energy barrier for one H2 molecule (with two postures) entering into the nanocage decreases from 435.59 (513.45) kcal/mol to 3.64(−2.06) kcal/mol with the increase of the truncated pore. The grand canonical Monte Carlo simulations reveal that each nanocage can accommodate only one H2 molecule inside its cavity at both 77 K and 298 K. All the other H2 molecules are adsorbed round the truncated pores outside the nanocages. Exceptionally, the truncated C46 can store 2.28wt% H2 molecules at 77K. Therefore, the truncating part of the C60 molecule may be a novel idea to explore C60 fullerene as a hydrogen storage material.

We report the application of customer-built scanning thermal microscopy (SThM) based on a commercial atomic force microscope to investigate local thermal inhomogeneity of ZnO varistors. The so-called 3ω method, generally used for measuring macroscale thermal conductivity, is set up and integrated with an atomic force microscope to probe the nanoscale thermal property. Remarkably, thermal contrasts of ZnO varistors are firstly imaged by the SThM, indicating the uniform distribution of spinel phases at triple points. The frequency-dependent thermal signal of ZnO varistors is also studied to present quantitative evaluation of local thermal conductivity of the sample.