Ga1-xMnxAs and related semiconductors are under intense investigation for the purpose of understandingthe ferromagnetism in these materials, pursuing higher TC, and, finally, for realizing semiconductor electronic devices that use both charge and spin. In this work, the electronic and magnetic structures of Ga1-xMnxAs (x＝3.125%, 6.25%, 12.5%, 25.0%, 50.0%） are studied by first-principles full-potential linearized augmented plane wave calculations with the generalized-gradient approximation. The ferromagnetic state is lower in energy than the paramagnetic and antiferromagnetic states. It is confirmed that Mn atoms stay magnetic with well localized magnetic moments. The calculated band structure shows that Mn doping also forms defect bands, and makes（Ga,Mn）As p-type conducting by providing holes. Furthermore, an s-d population inversion is found in the Mn electronic configuration, which results from the strong Mn p-d mixing. The induced As moments are substantial（about 20.15µB per Mn atom, and almost independent of x)—in accord with a recent observed negative As magnetic circular dichroism signal.

The recently reported room-temperature ferromagnetism in Cd1-xMnxGeP2 was investigated for x＝1.0,0.5, and 0.25 by the local density first-principles full-potential linearized augmented plane wave（FLAPW）and DMOL3 methods within both local-density approximation（LDA）and generalized gradient approximation (GGA). We find that the total energy of the antiferromagnetic（AFM）state is lower than the corresponding ferromagnetic (FM) state for all x studied. The GGA gives a better description of magnetic properties than LDA mainly due to its better prediction of structure, particularly for high Mn concentrations. The total spin moment of Cd1-xMnxGeP2 is～5.0µB per Mn atom. The FM alignment between Mn and Pincreases the total energy of the Mn-Mn FM coupling and makes the AFM ordering preferable.

Car、Parrinello首次提出的从头计算分子动力学方法有机地结合了密度泛函理论和分子动力学技术, 是目前计算机模拟实验中最先进最要的方法之一。本文简要地阐述了从头计算分子动力学方法的原理和具体实现, 以及近年来这一方法的发展和重要应用。

The influence of transition metals (TMs) on the hydriding/dedydriding critical point of NaAlH4 has been studied using the chemical potential method. The theoretical results predict that, if the reaction system reaches equilibrium, most of the TM additives significantly increase its hydriding/dedydriding critical point in the sequence Pd>Co>Zr>Ni>Nb>Hf>Ti>Mn>Fe>V>Cu>Cr and therefore have destabilizing effects on NaAlH4 in the same sequence. Experimentally, the isothermal dehydriding kinetics of NaAlH4 is studied only with Fe, Ti, and FeTi additives. The experimental results show that the destabilizing effect of Fe and Ti additives with coarse particles is very low while more effective destabilizing ability is achieved with fine FeTi particles. These experimental results suggest that the predicted destabilizing effect of TM additive is hindered kinetically due to the coarse particles of additives, and therefore experimental verification of the destabilizing effect of TMs should be performed with nanosized particles.

Zr mono-doped and (Zr,N) co-doped ZnO are investigated by the first-principles calculations. It is found that Zr prefers to substitute Zn site under most growth conditions. The passive (N-Zr-N) complexes create a fully occupied impurity band above the valence-band maximum (VBM) of ZnO, which helps p-type conductivity by reducing the ionization energy, consistent with a new approach to overcome the doping asymmetry [Y.F.Yan, J.B.Li, S.H.Wei, and M.M. Al-Jassim, Phys. Rev. Lett. 98 (2007) 135506]. In comparison with (Ga,N) co-doping, (Zr,N) is found to be probably better dopants to push p-type conductivity in ZnO through the new approach with easier formation of the passive impurity band.