Showing papers by "Francesco Mauri published in 1995"
TL;DR: The minimization of the functional with respect to overlapping localized orbitals can be performed so as to attain directly the ground-state energy, without being trapped at local minima, and allows one to improve the variational estimate of theGround- state energy, and the energy conservation during a molecular dynamics run.
Abstract: An energy functional for orbital-based O(N) calculations is proposed, which depends on a number of nonorthogonal, localized orbitals larger than the number of occupied states in the system, and on a parameter, the electronic chemical potential, determining the number of electrons. We show that the minimization of the functional with respect to overlapping localized orbitals can be performed so as to attain directly the ground-state energy, without being trapped at local minima. The present approach overcomes the multiple-minima problem present within the original formulation of orbital-based O(N) methods; it therefore makes it possible to perform O(N) calculations for an arbitrary system, without including any information about the system bonding properties in the construction of the input wave functions. Furthermore, while retaining the same computational cost as the original approach, our formulation allows one to improve the variational estimate of the ground-state energy, and the energy conservation during a molecular dynamics run. Several numerical examples for surfaces, bulk systems, and clusters are presented and discussed.
205 citations
TL;DR: This calculation provides evidence for self-trapping of the core exciton and gives a coherent interpretation of recent experimental x-ray absorption and emission data, predicting that self-Trapping should occur in the case of a valence biexciton.
Abstract: We present a first-principles study of excitonic self-trapping in diamond. Our calculation provides evidence for self-trapping of the core exciton and gives a coherent interpretation of recent experimental x-ray absorption and emission data. Self-trapping does not occur in the case of a single valence exciton. We predict, however, that self-trapping should occur in the case of a valence biexciton. This process is accompanied by a large local relaxation of the lattice which could be observed experimentally.
55 citations
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TL;DR: A general scheme for the computation of the time-dependent (TD) quadratic susceptibility of an extended insulator obtained by applying the ``2n+1'' theorem to the action functional as defined in TD density-functional theory is presented.
Abstract: We present a general scheme for the computation of the time dependent (TD) quadratic susceptibility ($\chi^{(2)}$) of an extended insulator obtained by applying the `$2n+1$' theorem to the action functional as defined in TD density functional theory. The resulting expression for $\chi^{(2)}$ includes self-consistent local-field effects, and is a simple function of the linear response of the system. We compute the static $\chi^{(2)}$ of nine III-V and five II-VI semiconductors using the local density approximation(LDA) obtaining good agreement with experiment. For GaP we also evaluate the TD $\chi^{(2)}$ for second harmonic generation using TD-LDA.
1 citations