Extreme anelastic responses (stiffness greater than diamond and large amplification of damping) due to the presence of a negative stiffness phase have been observed in Zn80Al20-BaTiO3 composites not only near the tetragonalorthorhombic transformation temperatures of BaTiO3 anticipated by the classical Landau theory, but far below the Curie point of BaTiO3 which can be manipulated via specific a...

Multiple inner-shell ionization of an atom in a heavy-ion collision and the vacancy rearrangement that follows are fundamental processes that so far have not been adequately described theoretically. The only fundamental theory of multiple inner-shell ionization whose results are widely available is the geometrical model [1]. It predicts that in central collisions (i.e. collisions restricted to ...

The age hardening of an Al-Mg-Si alloy was enhanced by the effect of high-speed (105 s11) compression prior to aging. This enhancement of the age hardening is brought about by the formation of vacancy clusters during high-speed compression. High resolution transmission electron microscopy reveals that these vacancy clusters form stacking fault tetrahedra. Following peak aging, vacancy clusters ...

A multilength scale method based on asymptotic expansion homogenization (AEH) is developed to compute minimum energy configurations of ensembles of atoms at the fine length scale and the corresponding mechanical response of the material at the coarse length scale. This multiscale theory explicitly captures heterogeneity in microscopic atomic motion in crystalline materials, attributed, for exam...

The role of oxygen vacancies in carbon dioxide electroreduction remains somewhat unclear. Here we construct a model of oxygen vacancies confined in atomic layer, taking the synthetic oxygen-deficient cobalt oxide single-unit-cell layers as an example. Density functional theory calculations demonstrate the main defect is the oxygen(II) vacancy, while X-ray absorption fine structure spectroscopy ...

As part of a multi-scale approach for modeling hydrogen embrittlement in hardened steels we have investigated, employing density functional theory methods, the stability and concentrations of the point defect clusters present in metastable Fe-C-H alloys with vacancies. The defect spectrum is found to be strongly dependent on the local vacancy concentration, and for low hydrogen levels sharp hig...

Monolayer molybdenum disulfide (MoS₂) has obtained much attention recently and is expected to be widely used in flexible electronic devices. Due to inevitable bending in flexible electronic devices, the structural and electronic properties would be influenced by tensile strains. Based on the density functional theory (DFT), the structural and electronic properties of monolayer MoS₂ with a sulfu...

Creating vacancy is often highly effective in enhancing the hydrogen evolution performance of transition metal-based catalysts. Vacancy-rich Ni nanosheets have been fabricated via topochemical formation two-dimentional (2D) Ni2B on graphene precursor followed by boron leaching. Anchored graphene, a few atomic layered are first obtained reduction and annealing. Large number vacancies then genera...

We have carried out a first-principles study on the nucleation and early-stage growth of He bubbles in Fe. The energetics, atomic and electronic structure of He-vacancy complexes, involving both a monovacancy and a nine-vacancy cluster, are examined. Based on the energetics, we then perform thermodynamics analysis to gain deeper insights into He bubble nucleation and growth. We have determined ...

Irradiation-induced vacancy defects in multiwalled (MW) boron nitride nanotubes (BNNTs) are investigated via in situ high-resolution transmission electron microscope operated at 80 kV, with a homogeneous distribution of electron beam intensity. During the irradiation triangle-shaped vacancy defects are gradually generated in MW BNNTs under a mediate electron current density (30 A cm(-2)), by kn...