R. Larico

Isolated nickel impurities in diamond: A microscopic model for the electrically active centers

We present a theoretical investigation on the structural and electronic properties of isolated nickel impurities in diamond. The atomic structures, symmetries, formation and transition energies, and hyperfine parameters of isolated interstitial and substitutional Ni were computed using ab initio total energy methods. Based on our results, we ultimately propose a consistent microscopic model which explains several experimentally identified nickel-related active centers in diamond.

Electronic properties and hyperfine fields of nickel-related complexes in diamond

We carried out a first principles investigation on the microscopic properties of nickel-related defect centers in diamond. Several configurations, involving substitutional and interstitial nickel impurities, have been considered either in isolated configurations or forming complexes with other defects, such as vacancies and boron and nitrogen dopants. The results, in terms of spin, symmetry, and hyperfine fields, were compared with the available experimental data on electrically active centers in synthetic diamond. Several microscopic models, previously proposed to explain those data, have been confirmed by this investigation, while some models could be discarded. We also provided new insights on the microscopic structure of several of those centers.

Spin states of iron impurities in magnesium oxide under pressure: A possible intermediate state

Ferropericlase (Mg,Fe)O is a major lower mantle mineral, and studying its properties is a fundamental step toward understanding the Earths interior. Here, we performed a first-principles investigation on the properties of iron as an isolated impurity in magnesium oxide, which is the condition of ferropericlase under which iron-iron interactions could be neglected. The calculations were carried using the all-electron full-potential linearized augmented plane wave method within the density functional theory in the generalized gradient approximation plus the on-site Hubbard correction. We present the electronic and magnetic properties, electric and magnetic hyperfine splitting of this impurity in high and low spin states for several charge states at zero pressure, which were then extended to high pressures. For the impurity in the neutral charge state, our results indicated that there is a metastable intermediate spin state (S=1), in addition to the high (S=2) and low (S=0) spin states. Those results were discussed in the context of an intermediate spin state, experimentally identified in ferrosilicate perovskite.

Microscopic structure of nickel-dopant centers in diamond

We present a theoretical investigation on the properties of interstitial nickel and its related complexes in diamond. The atomic configurations, symmetries, spins, and energetics of interstitial nickel, nickel-boron and nickel-vacancy complexes were investigated by a total energy ab initio methodology. Those results are used to explain certain electrically active centers, commonly found in synthetic diamond.

Cobalt-related impurity centers in diamond: electronic properties and hyperfine parameters

Cobalt-related impurity centers in diamond have been studied using first principles calculations. We computed the symmetry, formation and transition energies, and hyperfine parameters of cobalt impurities in isolated configurations and in complexes involving vacancies and nitrogen atoms. We found that the Co impurity in a divacant site is energetically favorable and segregates nitrogen atoms in its neighborhood. Our results are discussed in the context of the recently observed Co-related electrically active centers in synthetic diamond.

Nickel-Vacancy Complexes in Diamond: An Ab-Initio Investigation

The electronic and structural properties of nickel-vacancy complexes in diamond were investigated by a total energy ab initio methodology. These results are discussed in the context of the electrically active centers, commonly found in synthetic diamond.

Electronic properties of isolated nickel in diamond

Isolated nickel impurities in diamond have been investigated using the spin-polarized full-potential linearized augmented plane wave total energy method. The electronic and atomic structures, symmetries, transition energies, and formation energies of substitutional and interstitial Ni impurities in diamond were computed. The results were discussed in the context of the electrically active centers in synthetic diamond.