The metastability of vacancies was theoretically predicted for several compound semiconductors alongside their transformation into the antisite-vacancy pair counterpart; however, no experiment to date has unambiguously confirmed the existence of antisite-vacancy pairs. Using electron paramagnetic resonance and first principles calculations we identify the S15 center as the carbon antisite-vacan...

In this paper we report on the positron lifetime results obtained for brown and colourless natural diamond. Optical effects of the observed vacancy defects in brown, high pressure, high temperature (HPHT) treated colourless and naturally colourless type IIa diamond samples were studied by combining the positron measurement with monochromatic illumination. Brown diamond was found to contain opti...

In an effort to understand the behavior of hard materials in the presence of vacancies or impurities, we study the structural and electronic properties of diamond with specified vacancies. In our model, five carbon atoms in the shape of a centered tetrahedron are missing and 12 carbon atoms surrounding the vacancy are replaced by nitrogen or boron atoms. The bulk modulus of the material with ni...

Nitrogen-vacancy centers in diamond, being a promising candidate for quantum information processing, may also be an ideal platform for simulating many-body physics. However, it is difficult to realize interactions between nitrogen-vacancy centers strong enough to form a macroscopically ordered phase under realistic temperatures. Here we propose a scheme to realize long-range ferromagnetic Ising...

We study properties of vacancies in solid He using Path Integral Monte Carlo. We find, in agreement with other calculations, that the energy to create a single vacancy is 11.5K and is monotonic with the number of vacancies. If more the a few percent of the system becomes vacant, we find the system becomes unstable to melting. We show the number of exchanges in the system is increased by vacanci...

We apply a combination of positron annihilation spectroscopy and scanning tunneling microscopy to show that thermally generated P vacancies diffuse from the InP surface toward the bulk. The defect observed in the bulk can be identified as a complex consisting of a P vacancy and a Zn impurity. We infer that this pair is formed when the diffusing positive P vacancy is trapped at the Zn dopant. A ...

The enthalpy and entropy of vacancy creation in solid argon are re-evaluated using the two-body force approximation. At the triple point, the resulting vacancy free energy is g, = 1900 -4.0 RTcaljmole vat. This does not agree well with previous calculations of g,, but agrees well with experimental values of g, obtained from the argon specific heat”’ C, (but not with the questionable values obta...

We have studied the role of defects on the magnetic properties of carbon materials using first-principles density functional methods. We show that, while the total magnetization decreases both for diamond and graphite with increase in vacancy density, the magnetization decreases more rapidly for graphitic structures. The presence of nitrogen nearby a vacancy is shown to produce larger macroscop...

The correlation between thermal vacancy characteristics and D03 ordering in ball-milled nanocrystalline (Fe3Si)95Nb5 was studied by combined measurements of x-ray diffraction and positron annihilation. Structural stabilization due to grain boundary segregation of Nb enables high-temperature positron lifetime measurements up to 1023 K from which vacancy formation parameters identical to those in...

We develop a version of the vacancy mediated tracer diffusion model, which follows the properties of the physical system of In atoms diffusing within the top layer of Cu(0 0 1) terraces. This model differs from the classical tracer diffusion problem in that (i) the lattice is finite, (ii) the boundary is a trap for the vacancy, and (iii) the diffusion rate of the vacancy is different, in our ca...