We propose a computational method that drastically simplifies the inclusion of the spin–orbit interaction in density functional theory when implemented over localized basis sets. Our method is based on a well-known procedure for obtaining pseudopotentials from atomic relativistic ab initio calculations and on an on-site approximation for the spin–orbit matrix elements. We have implemented the technique in the SIESTA (Soler J M et al 2002 J. Phys.: Condens. Matter 14 2745–79) code, and show that it provides accurate results for the overall band-structure and splittings of group IV and III–IV semiconductors as well as for 5d metals.

Abstract. We propose a computational method that simplifies drastically the inclusion of spin-orbit interaction in density functional theory when implemented over localised atomic orbital basis sets. Our method is based on a well-known procedure for obtaining pseudopotentials from atomic relativistic ab initio calculations and on an on-site approximation for the spin-orbit matrix elements. We have implemented the technique in the SIESTA [34] code, and show that it provides accurate results for the overall band structure and splittings of group IV and III-IV semiconductors as well as for 5d metals.PACS numbers: 71.15. Ap,71.15.Dx,71.15.Rf,71.20.Be,71.20.Mq On-site Spin-orbit for LCAO 2

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Nitramine explosives can combine relative insensitivity to initiation and great energy content. In this work, based on a previous approach developed for nitroaromatic explosives, we propose four mathematical models to correlate impact sensitivity, given by the h50 value, to molecular charge properties. Fourteen cyclic nitramines were studied using Density Functional Theory (DFT). Six molecules of the set have measured h50 values, which were used to evaluate the sensitivity models. Converged DFT charge densities of the molecules were partitioned and analyzed according to the distributed multipole analysis (DMA) atom‐centered method. The sensitivity models were based on the DMA electric multipole values. The electron withdrawing role of the nitro group and the strong polarization of the charges of the nitrogen atom in the amine group were clearly identified. The influence of the electronic properties on the sensitivity of the explosives was characterized by including in the sensitivity models the charge values of the nitro or the nitramine groups and electron delocalization, the latter quantified by the DMA quadrupole values of the ring atoms. Inclusion of electron delocalization effects can improve the prediction of h50 values for two out of the five strained‐ring nitramines in the set. The charge values of the nitramine groups are the most important molecular property affecting the impact sensitivity. The h50 values of eight nitramine explosives of the set not available experimentally were computed.

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