The formation and migration of the vacancies in HCP metal Mg

The formation and migration energies of the mono- and di-vacancy in Mg crystal have been calculated using the modified analytical embedded atom method. The results show that, for mono-vacancy, the migration in the basal plane is slightly preferred to the migration out of the basal plane. For di-vacancy, the 1NN and 2NN configurations are not only easier to form but also more stable than the other configurations. The preferred migration mechanisms of the 1NN and 2NN di-vacancy are either invariable 1NN or 2NN configurations during migration in the basal plane or exchange 1NN for 2NN or 2NN for 1NN for migration out of the basal plane. These two-jump migration mechanisms of the di-vacancy, especially the former, are still preferred over the migration of the mono-vacancy. It is concluded that the greater the number of resting vicinity vacancies, the easier the migrating vacancy moves.     

Spin state selective Hadamard encoding during transfer periods using multiple selective CW-HCP

Hadamard spectroscopy today represents an alternative to conventional Fourier transform spectroscopy. The selective inversion of several narrow frequency bands is typically achieved by taylored inversion pulses in place of t1-evolution periods. However, band-selective inversion can also be achieved during coherence transfer steps, thereby shortening the period during which the magnetization is in the transverse plane. Using CW heteronuclear cross polarization (CW-HCP) as an example for highly selective coherence transfer, the implementation of Hadamard encoding within a transfer step is presented. Transfer characteristics, the preparation of multiple frequency selective CW-HCP and the possibility of acquiring spin state selective spectra are discussed in detail. The theoretical results are verified on two examples involving a cyclic pentapeptide and ubiquitin.     

The potential surface in the ground electronic state of HCP with the isomerization process: The validity of calculating potential surface with DFT methods

The density functional theory ( DFT) provides us an effective way to calculate large cluster systems with moderate computational demands. We calculate potential energy surfaces (PES) with several different approaches of DFT. The PES in the ground electronic state are related to HCP’s isomerization process. The calculated PES are compared with the ‘experimental’ PES obtained by fitting from the experimental vibrational spectra and that given by the ‘accurate’ quantum chemistry calculation with more expensive computations. The comparisons show that the potential surfaces calculated with DFT methods can reach the accuracy of less than 0.1 eV.     

The fundamental surface science of wurtzite gallium nitride

A review is presented that covers the experimental and theoretical literature relating to the preparation, electronic structure and chemical and physical properties of the surfaces of the wurtzite form of GaN. The discussion includes the adsorption of various chemical elements and of inorganic, organometallic and organic species. The focus is on work that contributes to a microscopic, atomistic understanding of GaN surfaces and interfaces, and the review concludes with an assessment of possible future directions.