Influence of excess charge on Platinum Clustering on graphene substrate
collaborators: Srinibas Nandi, Dr. Satadeep Bhattacharjee, Dr. Phani Motamarri
Platinum nanoparticles act as catalysts for the hydrogen evolution reaction in fuel cells, and the clustering of the Platinum nanoparticles reduces effective surface area and activity. We intend to study the influence of excess charge introduced by an electron gun on Platinum clustering on graphene sheet. To this end, this problem is modelled as a non-periodic system, allowing us to use the multipole boundary conditions in the Poisson problem to account for the non-zero net charge. As a first step, we employ the dftd4 to provide the empirical post-scf corrections to energy and forces to account for Van der Waals correction in the existing DFT-FE framework. By extending finite-element based methodologies for DFT to incorporate non-local Van der Waals functionals and long-range non-covalent interactions, we intend to more accurately capture the intricate surface chemistry processes and shed light on the mechanisms driving catalytic reactions at the atomic scale.
References
2019
JCP
A generally applicable atomic-charge dependent London dispersion correction
Eike Caldeweyher, Sebastian Ehlert, Andreas Hansen, and 4 more authors
The so-called D4 model is presented for the accurate computation of London dispersion interactions in density functional theory approximations (DFT-D4) and generally for atomistic modeling methods. In this successor to the DFT-D3 model, the atomic coordination-dependent dipole polarizabilities are scaled based on atomic partial charges which can be taken from various sources. For this purpose, a new charge-dependent parameter-economic scaling function is designed. Classical charges are obtained from an atomic electronegativity equilibration procedure for which efficient analytical derivatives with respect to nuclear positions are developed. A numerical Casimir-Polder integration of the atom-in-molecule dynamic polarizabilities then yields charge- and geometry-dependent dipole-dipole dispersion coefficients. Similar to the D3 model, the dynamic polarizabilities are precomputed by time-dependent DFT and all elements up to radon (Z = 86) are covered. The two-body dispersion energy expression has the usual sum-over-atom-pairs form and includes dipole-dipole as well as dipole-quadrupole interactions. For a benchmark set of 1225 molecular dipole-dipole dispersion coefficients, the D4 model achieves an unprecedented accuracy with a mean relative deviation of 3.8% compared to 4.7% for D3. In addition to the two-body part, three-body effects are described by an Axilrod-Teller-Muto term. A common many-body dispersion expansion was extensively tested, and an energy correction based on D4 polarizabilities is found to be advantageous for larger systems. Becke-Johnson-type damping parameters for DFT-D4 are determined for more than 60 common density functionals. For various standard energy benchmark sets, DFT-D4 slightly but consistently outperforms DFT-D3. Especially for metal containing systems, the introduced charge dependence of the dispersion coefficients improves thermochemical properties. We suggest (DFT-)D4 as a physically improved and more sophisticated dispersion model in place of DFT-D3 for DFT calculations as well as other low-cost approaches like semi-empirical models.
@article{caldeweyher_generally_2019,title={A generally applicable atomic-charge dependent {London} dispersion correction},volume={150},issn={00219606},url={https://doi.org/10.1063/1.5090222},doi={10.1063/1.5090222},number={15},urldate={2021-11-08},journal={Journal of Chemical Physics},author={Caldeweyher, Eike and Ehlert, Sebastian and Hansen, Andreas and Neugebauer, Hagen and Spicher, Sebastian and Bannwarth, Christoph and Grimme, Stefan},month=apr,year={2019},pmid={31005066},pages={154122},dimensions={true}}
2017
JCP
Extension of the D3 dispersion coefficient model
Eike Caldeweyher, Christoph Bannwarth, and Stefan Grimme
A new model, termed D4, for the efficient computation of molecular dipole-dipole dispersion coefficients is presented. As in the related, well established D3 scheme, these are obtained as a sum of atom-in-molecule dispersion coefficients over atom pairs. Both models make use of dynamic polarizabilities obtained from first-principles time-dependent density functional theory calculations for atoms in different chemical environments employing fractional atomic coordination numbers for interpolation. Different from the D3 model, the coefficients are obtained on-the-fly by numerical Casimir-Polder integration of the dynamic, atomic polarizabilities α(iω). Most importantly, electronic density information is now incorporated via atomic partial charges computed at a semi-empirical quantum mechanical tight-binding level, which is used to scale the polarizabilities. Extended statistical measures show that errors for dispersion coefficients with the proposed D4 method are significantly lower than with D3 and other, computationally more involved schemes. Alongside, accurate isotropic charge and hybridization dependent, atom-in-molecule static polarizabilities are obtained with an unprecedented efficiency. Damping function parameters are provided for three standard density functionals, i.e., TPSS, PBE0, and B3LYP, allowing evaluation of the new DFT-D4 model for common non-covalent interaction energy benchmark sets.
@article{caldeweyher_extension_2017,title={Extension of the {D3} dispersion coefficient model},volume={147},issn={0021-9606},url={http://dx.doi.org/10.1063/1.4993215},doi={10.1063/1.4993215},number={3},journal={The Journal of Chemical Physics},author={Caldeweyher, Eike and Bannwarth, Christoph and Grimme, Stefan},month=jul,year={2017},pmid={28734285},pages={034112},dimensions={true}}