Simulating Magnetic Circular Dichroism Spectra with Real-Time Time-Dependent Density Functional Theory in Gauge Including Atomic Orbitals

Abstract

Magnetic circular dichroism (MCD) spectra are able to provide insights into the geometric, electronic, and magnetic properties of chemical systems. However, they can be challenging to understand and simulate given the need to simultaneously treat both the finite magnetic and optical fields. Thus, efficient simulations are desired to understand the spectra and resolve the molecular electronic states. Real-time dynamics are used widely in the simulation of electronic spectroscopies such as absorption as well as electronic circular dichroism, but simulating MCD with real-time dynamics is technically and theoretically challenging. In this work, we introduce a real-time dynamics-based ab initio method with a nonperturbative treatment of a static magnetic field with London orbitals for simulating the MCD spectra of closed shell systems. Effects of a magnetic field are included variationally in the spin-free nonrelativistic Hamiltonian. Real-time time-dependent density functional theory dynamics are then performed, from which we compute the response function in the presence of the external magnetic field, giving the MCD spectrum. The method developed in this paper is applied to simulate the MCD spectra for pyrimidine, pyrazine, and 1,4-naphthoquinone. Results are discussed and compared to the experiment.

Efficient Four-Component Dirac-Coulomb-Gaunt Hartree--Fock in Pauli Spinor Representation

“…• The Pauli matrix representation is ideal for including external electromagnetic field perturbations, because the effects of each component of the electromagnetic field are completely decoupled and spin/component-separated. [22][23][24][25][26] • We also argue that the spin-separation in Pauli matrix representation allows for a clear understanding of how different types of spin physics, including two-electron spinfree, spin-orbit, and spin-spin interactions are manifested in electronic structure and light-matter coupling.…”

Magnetic circular dichroism within the Algebraic Diagrammatic Construction scheme of the polarisation propagator up to third order

“…77 These results have earlier provided a reference for theoretical investigations at different levels of theory. 18,23,32,[76][77][78] A TD-DFT study, 18 in particular, showed contradictory results with respect to the experimental data, which makes NQ and AQ interesting test cases for our MCD-ADC scheme. Given the size of NQ and AQ, only RICC2 and ADC(2) are considered.…”

“…Real-time approaches are also available to simulate MCD spectra, in particular at TD-DFT level. 31,32 The purpose of this study is to extend the portfolio of spectroscopies that can be simulated using the Algebraic Diagrammatic Construction (ADC) scheme of the polarization propagator 33 to include MCD. First introduced, in its second-order variant ADC(2), by Schirmer in 1984, 34 the ADC approach has the following two decades 35,36 found its primary applications to the investigation of photo-ionization processes 37,38 and to X-ray spectroscopy.…”

Polariton ring currents and circular dichroism of Mg-porphyrin in a chiral cavity

“…For MCD, we apply B = 8 T magnetic field along the x axis and simulate the CD spectrum with linear response TDDFT [55][56][57] using the same density functional and basis set used in TDA calculations.…”