Electron spectroscopies and inelastic processes in nanoclusters and solids: Theory and experiment

Aggelen

The Journal of Chemical Physics

2013

118

Double, Rydberg and charge transfer (CT) excitations have been great challenges for time-dependent density functional theory (TDDFT). Starting from an (N ± 2)-electron single-determinant reference, we investigate excitations for the N -electron system through the pairing matrix fluctuation, which contains information on twoelectron addition/removal processes. We adopt the particle-particle random phase approximation (pp-RPA) and the particle-particle Tamm

Section: Introductionmentioning

confidence: 99%

Double, Rydberg and charge transfer excitations from pairing matrix fluctuation and particle-particle random phase approximation

Aggelen

The Journal of Chemical Physics

2013

118

The Journal of Chemical Physics

“…After presenting experimental evidence of SiC formation at room temperature by electron spectroscopy of core (XPS) and valence bands (UPS) 3 on a Si(111) reconstructed (7×7) surface, our analysis will be mainly focused on the theoretical modeling of the C 60 cage rupture, which triggers all further chemical-physical processes. Furthermore, this investigation will enable us to envisage the role of the C 60 kinetic energy in initiating the SiC growth and driving the chemical reactions.…”

Section: Introductionmentioning

confidence: 99%

Non-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room temperature

Taioli

Garberoglio

Simonucci

et al. 2013

Self Cite

In this work, we investigate the processes leading to the room-temperature growth of silicon carbide thin films by supersonic molecular beam epitaxy technique. We present experimental data showing that the collision of fullerene on a silicon surface induces strong chemical-physical perturbations and, for sufficient velocity, disruption of molecular bonds, and cage breaking with formation of nanostructures with different stoichiometric character. We show that in these out-ofequilibrium conditions, it is necessary to go beyond the standard implementations of density functional theory, as ab initio methods based on the Born-Oppenheimer approximation fail to capture the excited-state dynamics. In particular, we analyse the Si-C 60 collision within the non-adiabatic nuclear dynamics framework, where stochastic hops occur between adiabatic surfaces calculated with time-dependent density functional theory. This theoretical description of the C 60 impact on the Si surface is in good agreement with our experimental findings.

“…2 The T -matrix elements appearing in Eq. (38) have been computed by means of multichannel scattering theory [28]. To perform this calculation we have included relativistic terms (of the order of 2 × 10 −6 a.u.…”

Section: Ab Initio Calculation Of the Multichannel T Matrixmentioning

confidence: 99%

“…Although the derivation of the main equations of our approach has been carried out in the T → 0 limit for the sake of conciseness, our theory can be straightforwardly extended to finite temperatures using Eq. (28). As a consequence, we can calculate the transition temperature T c -defined as (T c ) = 0-as a function of the parameter kr 0 .…”

Section: Finite-range Effects In the Unitary Limit For 6 LImentioning

confidence: 99%

Finite-range effects in dilute Fermi gases at unitarity

2011

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We develop a theoretical method going beyond the contact-interaction approximation frequently used in mean-field theories of many-fermion systems, based on the low-energy T matrix of the pair potential to rigorously define the effective radius of the interaction. One of the main consequences of our approach is the possibility to investigate finite-density effects, which are outside the range of validity of approximations based on δ-like potentials. We apply our method to the calculation of density-dependent properties of an ultracold gas of 6Li atoms at unitarity, whose two-body interaction potential is calculated using ab initio quantum chemistry methods. We find that density effects will be significant in ultracold gases with densities 1 order of magnitude higher than those attained in current experiments