Theoretical studies on magnetic circular dichroism by the finite perturbation method with relativistic corrections

Abstract

A theoretical method for calculating magnetic circular dichroism (MCD) of molecules is presented. We examined the numerical accuracy and the stability of the finite perturbation (FP) method and the sum-over-state (SOS) perturbation method. The relativistic effects are shown to be important for the MCD spectra of molecules containing heavy elements. Calculations using the FP and the SOS methods were carried out for ethylene, para- and ortho-benzoquinone, showing that the FP method is superior to the SOS method, as expected. The relativistic effect was examined using the second-order Douglas-Kroll Hamiltonians for the halogen molecules F2, Cl2, Br2, and I2. The Faraday terms of I2 and Br2 were strongly affected by the relativistic effects, while the effect was negligible for Cl2 and F2.

Fully relativistic calculations on the potential energy surfaces of the lowest 23 states of molecular chlorine

“…The SFR+ SO1 + SO2 result by Honda et al 32 is found to be significantly lower ͑2.88 eV͒, whereas the value found by Roszak and Lipinski for this state is considerably higher ͑3.38 eV͒ compared with our MRCISD+ Q result.…”

“…[20][21][22][23][24][25] The first ab initio potential curves for the Cl 2 molecule were computed by Peyerimhoff and Buenker 26 more than 25 years ago under the ⌳-⌺ approximation and served as the mainly theoretical basis for analysis of experimental data. Although semiempirical relativistic intermediate neglect of differential overlap ͑INDO͒ calculations were performed in Cl 2 15 years ago, 27 only recently, ab initio calculations including spin-orbit coupling have been performed [28][29][30][31][32][33] for some low lying valence states ͑usually͒ applying a relativistic core potential approach. Therefore, high accurate theoretical potential curves are of interest to understand Cl 2 spectra, as well as the analysis of nonadiabatic processes 34 and experimental data regarding the Cl 2 dissociation.…”

TD-DFT Investigation of the Magnetic Circular Dichroism Spectra of Some Purine and Pyrimidine Bases of Nucleic Acids

“…4,6,11,16, so-called complex polarization propagator (also known as damped response theory) methods 12,13,20 -as well as realtime methods 21 -have emerged in the last decade along with modern versions of sum-over-states approaches; 22,23 relativistic schemes have also been proposed. 24 We refer to Refs. 10 and 17 for reviews up to 2011.…”

Computation of magnetic circular dichroism by sum‐over‐states summations

“…SOS computational methods have been used relatively extensively for MCD computations in the past and are generally believed to be inconvenient for routine computations as they involve lengthy configuration interaction procedures . However, as shown below, this is not true for accurate excited states obtained from the TDDFT.…”