Many-body Approaches at Different Scales by G.G.N Angilella & C. Amovilli

Author:G.G.N Angilella & C. Amovilli
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

(16.12)

with the ‘local’ part given by the sum

(16.13)

and the ‘non local’ part, which accounts for projection over core angular momentum eigenfunctions, namely

(16.14)

by the radial functions

(16.15)

BFD pseudopotentials are very simple, are not singular and do not have a cusp at the origin, being designed for QMC calculations. These conditions are satisfied by the constraints

(16.16a)

(16.16b)

(16.16c)

These constraints must be preserved in the generation of core potential for fractional nuclear charges. The interpolation used in this study does not give well calibrated effective core potential but we consider this route as a reliable procedure to provide data not available from the literature. At the QMC level, we use a standard Slater–Jastrow (SJ) wavefunction with a Jastrow factor containing electron-nuclear, electron-electron, and electron-electron-nuclear terms [20]. At the variational Monte Carlo level (VMC), all parameters in our SJ wave functions are optimized by using the iterative linear method developed by Umrigar et al. [21]. At the diffusion Monte Carlo (DMC) level, performed in the fixed node approximation, the pseudopotentials are treated beyond the locality approximation using the T-move approach [22]. We used a time step of 0.05 a.u. in all the DMC calculations.

Finally, HF computations have been performed using the GAMESS-US package [23] while for QMC we used the CHAMP suite of programs [24].

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