Related papers: Structure stability in the simple element sodium u…
Recent high-pressure x-ray diffraction studies of alkali metals revealed unusual complex structures that follow the body-centered and face-centered cubic structures on compression. The structural sequence of potassium under compression to 1…
Alkali metals exhibit unexpected structures and electronic behavior at high pressures. Compression of metallic sodium (Na) to 200 GPa leads to the stability of a wide-band-gap insulator with the double hexagonal hP4 structure. Post-hP4…
Formation of the complex structure with 16 atoms in the orthorhombic cell, space group Cmca (Pearson symbol oC16) was experimentally found under high pressure in the alkali elements (K, Rb, Cs) and polyvalent elements of groups IV (Si, Ge)…
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…
Lithium - the lightest alkali metal - exhibits unexpected structures and electronic behaviour at high pressures. As the heavier alkalis, Li is bcc at ambient pressure and transforms first to fcc (at 7.5 GPa). The post-fcc high-pressure form…
The discovery of quasicrystals phases and approximants in Al(rich)-Mn system has revived the interest for complex aluminides containing transition-metal atoms. On one hand, it is now accepted that the Hume-Rothery stabilization plays a…
At ambient pressure, sodium, chlorine, and their only known compound NaCl, have well-understood crystal structures and chemical bonding. Sodium is a nearly-free-electron metal with the bcc structure. Chlorine is a molecular crystal,…
Crystal structures of simple metals and binary alloy phases based on the close-packed hexagonal structure are analyzed within the model of Fermi sphere-Brillouin zone interactions to understand distortions and superlattices. Examination of…
Binary alloy phases of the noble metals with main group elements are analyzed in relation to body centered cubic structure with orthorhombic and hexagonal distortions. Stability of these distorted phases is considered on the base of the…
The structures of compressed rubidium polyhydrides, RbHn with n>1, and their evolution under pressure are studied using density functional theory calculations. These phases, which start to stabilize at only P=2 GPa, consist of Rb+ cations…
In the search for MgB2-like phonon-mediated superconductors we have carried out a systematic density functional theory study of the Ca-B system, isoelectronic to Mg-B, at ambient and gigapascal pressures. A remarkable variety of candidate…
Results of X-ray diffraction experiments on solid oxygen at low temperature and at pressures up to 10 GPa are presented.A careful sample preparation and annealing around 240 K allowed to obtain very good diffraction patterns in the…
The binary (simple metal) phase diagram Au-Cd contains a number of intermetallic compounds with various distortions, superlattices and vacancies. To understand the reasons of these structural complexities and their phase stability, we…
The phase diagram and equation of state of dense nitrogen are of interest in understanding the fundamental physics and chemistry under extreme conditions, including planetary processes, and in discovering new materials. We predict several…
Alkali metals display unexpected properties at high pressure, including emergence of low symmetry crystal structures, that appear to occur due to enhanced electronic correlations among the otherwise nearly-free conduction electrons. We…
Based on its simple valence electron configuration, we may expect lithium to have straightforward physical properties that are easily explained. However, solid lithium, when cooled below 77 K, develops a complex structure that has been…
Group I/II materials exhibit unexpected structural phase transitions at high pressures, providing potential insight into the origins of elemental superconductivity. We present here a computational study of elemental barium and binary…
As titanium is a highly utilized metal for structural light-weighting, its phases, transformation pathways (transition states), and structures have scientific and industrial importance. Impurities, pressure, and temperature control the…
Evolutionary structure searches are used to predict a new class of compounds in the lithium--rich region of the lithium/hydrogen phase diagram under pressure. First principles computations show that LimH, 4<m<9, are stabilized with respect…
Group I elements - alkali metals Li, Na, K, Rb and Cs - are examples of simple metals with one s electron in the valence band. Under pressure these elements display unusually complex structural behaviour transforming from close-packed to…