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The band structures of Group IVB (Ti, Zr, Hf), VB (V, Nb, Ta) and V1B (Cr, Mo, W) transition metals and some of their carbides and nitrides (TiN, ZrN, HfN, VC, NbC, TaC, VN, NbN, TaN) with NaCl-type (Bl-type) structure have been calculated by using the tight-binding method within the Extended Huckel approximation (EHT). The energy bands, densities of states and crystal orbital overlap populations are given. The relationship between the bonding properties and the superconducting transition temperatures (Tc) of them is discussed. The influences of various kinds of metallic atoms and changes of bond lengths on Tc are also discussed.

A modified correlated spectroscopy (COSY) revamped with asymmetric Z-gradient echo detection sequence was designed to investigate the influence of diffusion behaviour on intermolecular double-quantum coherence signal attenuation during the pre-acquisition period. Theoretical formulas were deduced and experimental measurements and simulations were performed. It is found that the diffusion behaviour of intermolecular double-quantum coherence in the pre-acquisition period may be different from that of conventional single-quantum coherence, depending on the relative orientation of diffusion weighting gradients to coherence selection gradients. When the orientation of the diffusion weighting gradients is parallel or anti-parallel to the orientation of the coherence selection gradients, the diffusion is modulated by the distant dipolar field. This study is helpful for understanding the signal properties in intermolecular double-quantum coherence magnetic resonance imaging.

This paper analyses the heteronuclear Cosy Revamped by Asymmetric Z-gradient Echo Detection pulse sequence. General theoretical expressions of the pulse sequence with arbitrary flip angles were derived by using dipolar field treatment and signals originating from heteronuclear intermolecular single-quantum coherences (iSQCs) in highly-polarized two spin-1/2 systems were mainly discussed in order to find the optimal flip angles. The results show that signals from heteronuclear iSQCs decay slower than those from intermolecular double-quantum coherences or intermolecular zero-quantum coherences. Magical angle experiments validate that the signals are from heteronuclear iSQCs and insensitive to the imperfection of radio-frequency flip angles. All experimental observations are in excellent agreement with theoretical predictions. The quantum-mechanical treatment leads to similar predictions to the dipolar field treatment.

The solvent peak in the intermolecular multiple-quantum coherence spectra can be suppressed by either applying pulse field gradients or spinning sample along the magic angle direction ( = 54.7). However, these two methods also suppress the signals of the solute. We design two pulse sequences with only z-axis gradients to suppress the solvent peak without reducing the intensity of solute signals. Compared to the former pulse sequence, the latter pulse sequence is insensitive to the imperfection of pulse flip angles. When the flip angles of the second pulse sequence are purposely deviated 1/10 from the optimal values, the solvent peak is still weak. Theoretical expressions, experimental observations and computer simulations demonstrate that the two methods can be used to effectively suppress solvent peak in intermolecular multiple-quantum coherence spectra.

Electron structure of three series of alloy heterojunctions (GaAs)x(Ge2)1-x/Ge,(AlAs)x(Ge2)1-x/Ge and AlxG1-xAs/Ge are calculated by linear muffin-tin orbital method with atomic-sphere approximation using the average-bond-energy theory in conjunction with a cluster expansion method. The results indicate the variations of ΔEν(x) at heterojunctions (GeAs)x(Ge2)1-x/Ge and (AlAs)x(Ge2)1-x/Ge are nonlinear, which are very different from that of AlxGa1-xAs/Ge.

We have extended the average-bond-energy method to the study of strained-layer heterojunction band offset. Through a careful study of the effect of hydrostatic strain and uniaxial strain on band offset parameter Emv, we find that the average band offset parameter Emv,av(Emv,av=Em-Ev,av) is largely kept unchanged under different strain conditions. So, in the calculation of strained-layer band offset parameter Emv, it is only required the unstrained band offset parameter Emv,0, a deformation parameter b and the experimental value of spin-orbit splitting Δ0 to calculate the value of strained-layer Emv by simple algebraic operation. Obviously, it will be very convenient to calculate the valence band offset of heterojunction. The simplifed calculation scheme has the characteristic of small calculation amount and the calculation reliability can be improved by using the experimental value.