We have investigated band structures of a series of 28 ternary half-Heusler compounds MMЈX of MgAgAs type, where M = ͑Lu, La, Sc, Y͒ and MЈX = ͑PtBi, AuPb, PdBi, PtSb, AuSn, NiBi, PdSb͒. Our results show that the Z 2 topological order is due to a single band inversion at the ⌫ point. In native states, these half-Heusler compounds are identified as being topologically nontrivial semimetals, or nontrivial metals, or trivial insulators, which can be turned into insulating thin films on suitable substrates. Our analysis reveals a straightforward relationship which connects the band inversion strength ͑extent of deviation from the critical point͒ to the atomic charge of constituents and the lattice parameter. Our findings suggest a general method for identifying Z 2 topological insulators in nonmagnetic ternary compounds.

The high-temperature superconducting cuprate La(2-x)Sr(x)CuO(4) (LSCO) shows several phases ranging from antiferromagnetic insulator to metal with increasing hole doping. To understand how the nature of the hole state evolves with doping, we have carried out high-resolution Compton scattering measurements at room temperature together with first-principles electronic structure computations on a series of LSCO single crystals in which the hole doping level varies from the underdoped (UD) to the overdoped (OD) regime. Holes in the UD system are found to primarily populate the O 2p(x)/p(y) orbitals. In contrast, the character of holes in the OD system is very different in that these holes mostly enter Cu d orbitals. High-resolution Compton scattering provides a bulk-sensitive method for imaging the orbital character of dopants in complex materials.

Positron annihilation lifetime spectroscopy and positron-electron momentum density (PEMD) studies on multilayers of PbSe nanocrystals (NCs), supported by transmission electron microscopy, show that positrons are strongly trapped at NC surfaces, where they provide insight into the surface composition and electronic structure of PbSe NCs. Our analysis indicates abundant annihilation of positrons with Se electrons at the NC surfaces and with O electrons of the oleic ligands bound to Pb ad-atoms at the NC surfaces, which demonstrates that positrons can be used as a sensitive probe to investigate the surface physics and chemistry of nanocrystals inside multilayers. Ab initio electronic structure calculations provide detailed insight in the valence and semi-core electron contributions to the positron-electron momentum density of PbSe. Both lifetime and PEMD are found to correlate with changes in the particle morphology characteristic of partial ligand removal

We have studied the [100]- [110] anisotropy of the Compton profile in the bilayer manganite. Quantitative agreement is found between theory and experiment with respect to the anisotropy in the two metallic phases (i.e. the low temperature ferromagnetic and the colossal magnetoresistant phase under a magnetic field of 7 T). Robust signatures of the metal-insulator transition are identified in the momentum density for the paramagnetic phase above the Curie temperature. We interpret our results as providing direct evidence for the transition from the metallic-like to the admixed ioniccovalent bonding accompanying the magnetic transition. The number of electrons involved in this phase transition is estimated from the area enclosed by the Compton profile anisotropy differences. Our study demonstrates the sensitivity of the Compton scattering technique for identifying the number and type of electrons involved in the metal-insulator transition. [5,6]. Above T c , the phase diagram displays an insulating paramagnetic (PM) phase. The Mn-3d electronic states, which are responsible for these properties, split into e g and t 2g contributions in the crystal field of the MnO 6 octahedron. The FM phase below T c and its metallic conductivity are usually explained on the basis of the double exchange (DE) mechanism [7], where e g electrons hop between Mn sites through hybridization with the oxygen 2p orbitals and align the localized t 2g spins by the exchange interaction. While the DE mechanism appears to capture the tendency towards ferromagnetism, it still remains unclear if oxygen orbitals should be explicitly included in the electronic degrees of freedom, or whether they can be integrated out as is often assumed in the standard models [8,9].Recent magnetic Compton scattering (MCS) studies [10] of the manganite FM phase have shown how the occupation numbers of the e g states vary with doping [11,12] as well as temperature [13,14]. In addition, they have provided evidence for the coexistence of localized and itinerant e g magnetic electrons [15,16] in the FM phase. MCS has also been used to study other spintronics materials such as magnetite Fe 3 O 4 and its mysterious Verwey transition [17].In this letter, we show that the anisotropy of high resolution Compton profiles (CP) displays a striking difference between the insulating PM and metallic FM case. This is important because this difference originates in the MnO planes which are the seat of the CMR properties. Similar effects have been observed in the metallic YBa 2 Cu 3 O 7 and insulating PrBa 2 Cu 3 O 7 systems [18]. However, this is the first time that this effect has been observed on the same sample under the influence of external parameters such as temperature and magnetic field. We also provide a measure of the number of electrons involved in the CMR effect.Compton scattering, or inelastic scattering with very

Xanthine Oxidoreductase (XOR) exists in a variety of organisms from bacteria to humans and catalyzes the oxidation of hypoxanthine to xanthine and from xanthine to uric acid. Excessive uric acid could lead to gout and hyperuricemia. In this paper, we have reviewed the recent computational studies on xanthine oxidase inhibition. Computational methods, such as molecular dynamics (molecular mechanics), quantum mechanics, and quantum mechanics/molecular mechanics (QM/MM), have been employed to investigate the binding affinity of xanthine oxidase with synthesized and isolated nature inhibitors. The limitations of different computational methods for xanthine oxidase inhibition studies were also discussed. Implications of the computational approach could be used to help to understand the existing arguments on substrate/product orientation in xanthine oxidase inhibition, which allows designing new inhibitors with higher efficacy.