Computational prediction of new magnetic materials.

The discovery of new magnetic materials is a big challenge in the field of modern materials science. We report the development of a new extension of the evolutionary algorithm USPEX, enabling the search for half-metals (materials that are metallic only in one spin channel) and hard magnetic materials. First, we enabled the simultaneous optimization of stoichiometries, crystal structures, and magnetic structures of stable phases.

Programmable nano-reactors for stochastic sensing.

Chemical reactions of single molecules, caused by rapid formation or breaking of chemical bonds, are difficult to observe even with state-of-the-art instruments. A biological nanopore can be engineered into a single molecule reactor, capable of detecting the binding of a monatomic ion or the transient appearance of chemical intermediates. Pore engineering of this type is however technically challenging, which has significantly restricted further development of this technique.

Correction: The stability and unexpected chemistry of oxide clusters.

Correction for 'The stability and unexpected chemistry of oxide clusters' by Xiaohu Yu et al., Phys. Chem.

The stability and unexpected chemistry of oxide clusters.

Using evolutionary structure prediction and ab initio thermodynamics, we determine stable compositions and structures of small CemOn and FemOn clusters at realistic temperatures and oxygen pressures. We use second energy differences as the criterion determining clusters of particular stability ("magic" clusters), whereas HOMO-LUMO gaps are used to gauge chemical inertness - i.e.

Mechanism of the fcc-to-hcp phase transformation in solid Ar.

We present an atomistic description of the fcc-to-hcp transformation mechanism in solid argon (Ar) obtained from transition path sampling molecular dynamics simulation. The phase transition pathways collected during the sampling for an 8000-particle system reveal three transition types according to the lattice deformation and relaxation details. In all three transition types, we see a critical accumulation of defects and uniform growth of a less ordered transition state, followed by a homogeneous growth of an ordered phase.

A stable compound of helium and sodium at high pressure.

Helium is generally understood to be chemically inert and this is due to its extremely stable closed-shell electronic configuration, zero electron affinity and an unsurpassed ionization potential. It is not known to form thermodynamically stable compounds, except a few inclusion compounds. Here, using the ab initio evolutionary algorithm USPEX and subsequent high-pressure synthesis in a diamond anvil cell, we report the discovery of a thermodynamically stable compound of helium and sodium, NaHe, which has a fluorite-type structure and is stable at pressures >113 GPa.

Diverse Chemistry of Stable Hydronitrogens, and Implications for Planetary and Materials Sciences.

Nitrogen hydrides, e.g., ammonia (NH3), hydrazine (N2H4) and hydrazoic acid (HN3), are compounds of great fundamental and applied importance.

Combined Theoretical and in Situ Scattering Strategies for Optimized Discovery and Recovery of High-Pressure Phases: A Case Study of the GaN-Nb2O5 System.

The application of pressure in solid-state synthesis provides a route for the creation of new and exciting materials. However, the onerous nature of high-pressure techniques limits their utility in materials discovery. The systematic search for novel oxynitrides-semiconductors for photocatalytic overall water splitting-is a representative case where quench high-pressure synthesis is useful and necessary in order to obtain target compounds.

Novel superhard B-C-O phases predicted from first principles.

We explored the B-C-O system at pressures in the range 0-50 GPa by ab initio variable-composition evolutionary simulations in the hope of discovering new stable superhard materials. A new tetragonal thermodynamically stable phase B4CO4, space group I4[combining macron], and two low-enthalpy metastable compounds (B6C2O5, B2CO2) have been discovered. Computed phonons and elastic constants show that these structures are dynamically and mechanically stable both at high pressure and zero pressure.

Antiferromagnetic Stabilization in the Ti8O12 Cluster.

Using the evolutionary algorithm USPEX and DFT+U calculations, we predicted a high-symmetry geometric structure of the bare Ti8 O12 cluster composed of 8 Ti atoms forming a cube, in which O atoms are at midpoints of all of its edges, in excellent agreement with experimental results. Using natural bond orbital analysis, adaptive natural density partitioning algorithm, electron localization function, and partial charge plots, we find the origin of the particular stability of bare Ti8 O12 cluster: unique chemical bonding where eight electrons of Ti atoms interacting with each other in antiferromagnetic fashion to lower the total energy of the system. The bare Ti8 O12 is thus an unusual molecule stabilized by d-orbital antiferromagnetic coupling.

Nitrogen oxides under pressure: stability, ionization, polymerization, and superconductivity.

Nitrogen oxides are textbook class of molecular compounds, with extensive industrial applications. Nitrogen and oxygen are also among the most abundant elements in the universe. We explore the N-O system at 0 K and up to 500 GPa though ab initio evolutionary simulations.

A novel phase of beryllium fluoride at high pressure.

A previously unknown thermodynamically stable high-pressure phase of BeF2 has been predicted using the evolutionary algorithm USPEX. This phase occurs in the pressure range 18-27 GPa. Its structure has C2/c space group symmetry and contains 18 atoms in the primitive unit cell.

Backbone NxH compounds at high pressures.

Optical and synchrotron x-ray diffraction diamond anvil cell experiments have been combined with first-principles theoretical structure predictions to investigate mixtures of N2 and H2 up to 55 GPa. Our experiments show the formation of structurally complex van der Waals compounds [see also D. K.

The phase diagram and hardness of carbon nitrides.

Novel superhard materials, especially those with superior thermal and chemical stability, are needed to replace diamond. Carbon nitrides (C-N), which are likely to possess these characteristics and have even been expected to be harder than diamond, are excellent candidates. Here we report three new superhard and thermodynamically stable carbon nitride phases.

Novel hydrogen hydrate structures under pressure.

Gas hydrates are systems of prime importance. In particular, hydrogen hydrates are potential materials of icy satellites and comets, and may be used for hydrogen storage. We explore the H₂O-H₂ system at pressures in the range 0-100 GPa with ab initio variable-composition evolutionary simulations.

Pressure-induced stabilization and insulator-superconductor transition of BH.

Diborane (B(2)H(6)), a high energy density material, was believed to be stable in a wide P, T interval. A systematic investigation of the B-H system using the ab initio variable-composition evolutionary simulations shows that boron monohydride (BH) is thermodynamically stable and can coexist with solid B, H(2), and B(2)H(6) in a wide pressure range above 50 GPa. B(2)H(6) becomes unstable and decomposes into the Ibam phase of BH and H(2) (C2/c) at 153 GPa.

An ab initio study on the transition paths from graphite to diamond under pressure.

We calculate and compare the transition paths from graphite to two types of diamond using the variable cell nudged elastic band method. For the phase transition from graphite to cubic diamond, we analyze in detail how the π bonds transit to the σ bonds in an electronic structure. Meanwhile, a new transition path with a lower energy barrier for the transformation from graphite to hexagonal diamond is discovered.

First-principles determination of the structure of magnesium borohydride.

The energy landscape of Mg(BH(4))(2) under pressure is explored by ab initio evolutionary calculations. Two new tetragonal structures, with space groups P4 and I4(1)/acd, are predicted to be lower in enthalpy by 15.4 and 21.

FastUniq: a fast de novo duplicates removal tool for paired short reads.

The presence of duplicates introduced by PCR amplification is a major issue in paired short reads from next-generation sequencing platforms. These duplicates might have a serious impact on research applications, such as scaffolding in whole-genome sequencing and discovering large-scale genome variations, and are usually removed. We present FastUniq as a fast de novo tool for removal of duplicates in paired short reads.