Quantum Modelling Group

The Quantum Modeling group uses density functional theory methods to study the interactions, stability, electronic structure and excited states of various types of materials. New methods have been developed within the range-separated hybrid DFT scheme, which combine short-range DFT and long-range Hartree-Fock and MP2 or RPA  description of the electron-electron interactions. These approaches are well-adapted to remedy the well-know failure of local and semi-local functionals to simulate van der Waals, and in particular London dispersion forces, which can eb associated with long-range dynamic electron correlation effects. The various electronic states of materials are simulated with advanced technologies, like GW, BSE and TDDFT methods.

Highlights

  • New algorithms for RPA

Random-phase approximation correlation energies from Lanczos chains and an optimal basis set: Theory and applications to the benzene dimer D. Rocca, J. Chem. Phys., 140 (2014) 18A501.

benzene-dimerA new ab initio approach is introduced to compute the correlation energy within the adiabatic connection fluctuation dissipation theorem in the random phase approximation. First, an optimally small basis set to represent the response functions is obtained by diagonalizing an approximate dielectric matrix containing the kinetic energy contribution only. Then, the Lanczos algorithm is used to compute the full dynamical dielectric matrix and the correlation energy. The convergence issues with respect to the number of empty states or the dimension of the basis set are avoided and the dynamical effects are easily kept into account. To demonstrate the accuracy and efficiency of this approach the binding curves for three different configurations of the benzene dimer are computed: T-shaped, sandwich, and slipped parallel.

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