arXiv subjects

Joydev De

Publications and source records attributed to Joydev De.

3 recordsLinked to original sources

arXiv2023

Optical excitation from anti-causally corrected real-time dynamics in a minimal basis

Here we demonstrate workably accurate estimation of optical excitation threshold for large systems comprising of hundreds of atoms through an anti-causally corrected(ACC) real-time dynamics(RTD) approach implemented in a minimal tight-binding basis constituted by the directed hybrid atomic Wannier orbitals. A correction to the Hamiltonian is applied anti-causally at all time steps to account for electron-hole interaction using the density-density response function. Minimality of basis and ease of transferability of parameters to large systems arises from the directed nature of the Wannierized hybrid basis orbitals used.With self-energy corrected TB parameters evaluated at the DFT + G 0 W 0 level, the proposed ACC-RTD scheme can be systematically parametrized to render optical excitation threshold for systems of experimentally realizable length-scales through inexpensive computation.

cond-mat.mtrl-sci↗

arXiv2022

Maximally valent orbitals in systems with non-ideal bond-angles

In pursuit of a minimal basis for systems with non-ideal bond angles, in this work we try to pinpoint the exact orientation of the major overlapping orbitals along the nearest neighbouring coordination segments in a given system such that they maximally represent the covalent interactions through out the system. We compute Mayer's bond order, akin to the Wiberg's bond index, in the basis of atomic Wannier orbitals with customizable non-degenerate hybridization constructed from first principles, in a representative variety of molecules and layered systems. We put them in perspective with unbiased maximally localized descriptions of bonding and non-bonding orbitals, and energetics to tunneling of electrons through them between nearest neighbours, to describe the different physical aspects of covalent interactions, which are not necessarily represented by a single unique set of atomic or bonding orbitals.

cond-mat.mtrl-sci↗

arXiv2020

Hybrid atomic orbital basis from first principles: Bottom-up mapping of self-energy correction to large covalent systems

Construction of hybrid atomic orbitals is proposed as the approximate common eigen states of finite first moment matrices. Their hybridization and orientation can be a-priori tunned as per their anticipated neighbourhood. Their Wannier function counterparts constructed from the Kohn-Sham(KS) single particle states constitute an orthonormal multi-orbital tight-binding(TB) basis resembling hybrid atomic-orbitals locked to their immediate atomic neighborhood, while spanning the subs-space of KS states. The proposed basis thus not only renders predominantly single TB parameters from first-principles for each nearest neighbour bonds involving no more than two orbitals irrespective of their orientation, but also facilitate an easy route for transfer of such TB parameters across isostructural systems exclusively through mapping of neighbourhoods and projection of orbital charge centres. With hybridized 2s,2p and 3s,3p valence electrons, the spatial extent of self-energy correction(SEC) to TB parameters in the proposed basis are found to be localized mostly within the third nearest neighbourhood, thus allowing effective transfer of self-energy corrected TB parameters from smaller reference systems to much larger target systems, with nominal additional computational cost beyond that required for explicit computation of SEC in the reference systems. The proposed approach promises inexpensive estimation of quasi-particle structure of large covalent systems with workable accuracy.

cond-mat.mtrl-sci↗