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Ke S.-H.,Tongji University | Ke S.-H.,Beijing Computational Science Research Center
Physical Review B - Condensed Matter and Materials Physics

An efficient all-electron G0W0 method and a quasiparticle self-consistent GW (QSGW) method for molecules are proposed in the molecular-orbital space with the full random-phase approximation. The convergence with the basis set is examined. As an application, the ionization energy and electron affinity of a series of conjugated molecules (up to 32 atoms) are calculated and compared to the experiment. The QSGW result improves the G0W0 result and both of them are in significantly better agreement with experimental data than those from Hartree-Fock (HF) and hybrid density-functional calculations, especially for electron affinity. The nearly correct energy gap and suppressed self-interaction error by the HF exchange make our method a good candidate for investigating electronic and transport properties of molecular systems. © 2011 American Physical Society. Source

Miao M.-S.,Beijing Computational Science Research Center | Miao M.-S.,University of California at Santa Barbara | Hoffmann R.,Cornell University
Accounts of Chemical Research

ConspectusElectrides, in which electrons occupy interstitial regions in the crystal and behave as anions, appear as new phases for many elements (and compounds) under high pressure. We propose a unified theory of high pressure electrides (HPEs) by treating electrons in the interstitial sites as filling the quantized orbitals of the interstitial space enclosed by the surrounding atom cores, generating what we call an interstitial quasi-atom, ISQ.With increasing pressure, the energies of the valence orbitals of atoms increase more significantly than the ISQ levels, due to repulsion, exclusion by the atom cores, effectively giving the valence electrons less room in which to move. At a high enough pressure, which depends on the element and its orbitals, the frontier atomic electron may become higher in energy than the ISQ, resulting in electron transfer to the interstitial space and the formation of an HPE.By using a He lattice model to compress (with minimal orbital interaction at moderate pressures between the surrounding He and the contained atoms or molecules) atoms and an interstitial space, we are able to semiquantitatively explain and predict the propensity of various elements to form HPEs. The slopes in energy of various orbitals with pressure (s > p > d) are essential for identifying trends across the entire Periodic Table. We predict that the elements forming HPEs under 500 GPa will be Li, Na (both already known to do so), Al, and, near the high end of this pressure range, Mg, Si, Tl, In, and Pb. Ferromagnetic electrides for the heavier alkali metals, suggested by Pickard and Needs, potentially compete with transformation to d-group metals. © 2014 American Chemical Society. Source

Chen L.-B.,Qingdao Technological University | Yang W.,Beijing Computational Science Research Center
Laser Physics Letters

We propose a two-qubit optically controlled phase gate in quantum dot molecules via adiabatic passage and hole tunnelling. Our proposal combines the merits of the current generation of vertically stacked self-assembled InAs quantum dots and adiabatic passage. The simulation shows an implementation of the gate with a fidelity exceeding 0.98. © 2014 Astro Ltd. Source

Chen M.,Fudan University | You J.Q.,Beijing Computational Science Research Center
Physical Review A - Atomic, Molecular, and Optical Physics

Non-Markovian quantum state diffusion (NMQSD) provides a powerful approach to the dynamics of an open quantum system in bosonic environments. Here we develop a NMQSD method to study the open quantum system in fermionic environments. This problem involves anticommutative noise functions (i.e., Grassmann variables) that are intrinsically different from the noise functions of bosonic baths. We obtain the NMQSD equation for quantum states of the system and the non-Markovian master equation. Moreover, we apply this NMQSD method to single- and double-quantum-dot systems. © 2013 American Physical Society. Source

Chen Y.,Beijing Computational Science Research Center
Physical Review A - Atomic, Molecular, and Optical Physics

We investigate the high-order harmonic generation of atoms and molecules exposed in strong and short-wavelength (shorter than 800 nm) laser fields. Our simulations show that the electronic rescattering trajectory depends strongly on the property of the Coulomb potential. Using numerical schemes, we identify the important role of excited states in the emission times of harmonics from molecules. We propose a model, which considers the initial position when electrons tunnel out from the potential, to explain the electronic response in intense and relatively high-frequency laser fields. © 2011 American Physical Society. Source

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