arXiv subjects

Omololu Akin-Ojo

Publications and source records attributed to Omololu Akin-Ojo.

5 recordsLinked to original sources

arXiv2025

Excitation energies and UV-Vis absorption spectra from INDO/s+ML

The semi-empirical INDO/s method is popular for studies of excitation energies and absorption of molecules due to its low computational requirement, making it possible to make predictions for large systems. However, its accuracy is generally low, particularly, when compared with the typical accuracy of other methods such as time-dependent density functional theory (TDDFT). Here, we present machine learning (ML) models that correct the INDO/s results with negligible increases in the amount of computing resources needed. While INDO/s excitations energies have an average error of about 1.1 eV relative to TDDFT energies, the added ML corrections reduce the error to 0.2 eV. Furthermore, this combination of INDO/s and ML produces UV-Vis absorption spectra that are in good agreement with the TDDFT predictions.

cond-mat.mes-hall↗

arXiv2025

The impossibility of expanding the square root of the electron density as a linear combination of elements of a complete set of basis functions

In orbital-free density functional theory (OFDFT), an equation exists for $ψ= \sqrt n$, the square root of the ground state electron density $n$. We show that $ψ$ cannot be expanded as a linear combination of elements of a complete set of basis functions except in the case of one or two electron systems. This is unlike the case for the ground state of a system of identical bosons in which the square root of the ground state bosonic density can have an expansion as a linear combination of elements of a complete set of basis functions.

physics.chem-ph↗

arXiv2022

Electronic Structure and Magnetism of the Triple-layered Ruthenate Sr$_{4}$Ru$_{3}$O$_{10}$

We report electronic band structure calculations for Sr$_{4}$Ru$_{3}$O$_{10}$ that displays both ferromagnetic and metamagnetic behavior. The density functional calculations find the ground state to be ferromagnetic in agreement with the experiment and we find that the inclusion of Coulomb Hubbard interaction U applied to the Ru 4d states has dramatic effects on the Fermi surface, which reveal the role of Coulomb interactions and correlated many-body physics. The minority spin bands are mainly empty with Fermi surfaces in the outer areas of the Brillouin zone away from the $Γ$ point with bands that disperse steeply upward. The majority spin bands are full or nearly fully occupied and form narrow bands near the Fermi energy around the $Γ$ point, which could be the electronic origin of the metamagnetism. The results are in qualitative agreement with recent angle resolved photoemission spectroscopy (ARPES) experiments and show the need for a combined theoretical study and experimental ARPES investigation with better energy resolution to reveal the nature of the narrow bands close to the Fermi-level, which is critical for understanding the exotic magnetic properties observed in this material.

cond-mat.str-el↗

arXiv2015

First Principles Predictions of Superconductivity in Doped Stanene

Stanene, composed of tin atoms arranged in a single layer, is the tin analogue of graphene and past studies predicted it to be a topological insulator. An energy band gap (of $\sim 0.1$~eV) was obtained in previous calculations for the buckled honeycomb structure of stanene and, thus, phonon-mediated superconductivity in this material is ruled out. In this work we investigated, from first principles calculations within density functional theory (DFT), the possibility of producing phonon-mediated superconductivity in stanene by doping the material. It was found that doping with calcium (lithium) leads to superconductivity, albeit, with a very low superconducting transition temperature $T_c$ of $\sim 0.7$~K ($\sim 1.3$~K), even lower than the value ($3.7$~K) for bulk $β$-Tin.

cond-mat.supr-con↗

arXiv2013

Phase controlling current reversals in a chaotic ratchet transport

We consider a deterministic chaotic ratchet model for which the driving force is designed to allow the rectification of current as well as the control of chaos of the system. Besides the amplitude of the symmetric driving force which is often used in this framework as control parameter, a phase has been newly included here. Exploring this phase, responsible of the asymmetry of the driven force, a number of interesting departures have been revealed. Remarkably, it becomes possible to drive the system into one of the following regime: the state of zero transport, the state of directed transport and most importantly the state of reverse transport (current reversal). To have a full control of the system, a current reversal diagram has been computed thereby clearly showing the entire transport spectrum which is expected to be of interest for possible experiments in this model.

nlin.CD↗