Excitation Energies from Real-Time Propagation of the Four-Component Dirac–Kohn–Sham Equation

Repiský, Michal; Konecny, Lukas; Kadek, Marius; Komorovský, Stanislav; Malkin, Olga L.; Malkin, Vladimir G.; Ruud, Kenneth

doi:10.1021/ct501078d

Cited by 89 publications

(187 citation statements)

References 71 publications

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“…All these DFT results were obtained using a development version of the program package ReSpect. 53 Additional test calculations for LiI, NaF, and RbBr were also performed at the SO-ZORA level, using the Amsterdam Density Functional (ADF) 54 program package employing the PBE0 48 functional together with the JCPL 6 basis set.…”

Section: Methodsmentioning

confidence: 99%

Indirect NMR spin–spin coupling constants in diatomic alkali halides

Jaszuński

Antušek

Demissie

et al. 2016

The Journal of Chemical Physics

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We report the Nuclear Magnetic Resonance (NMR) spin-spin coupling constants for diatomic alkali halides MX, where M = Li, Na, K, Rb, or Cs and X = F, Cl, Br, or I. The coupling constants are determined by supplementing the non-relativistic coupled-cluster singles-and-doubles (CCSD) values with relativistic corrections evaluated at the four-component density-functional theory (DFT) level. These corrections are calculated as the differences between relativistic and non-relativistic values determined using the PBE0 functional with 50% exact-exchange admixture. The total coupling constants obtained in this approach are in much better agreement with experiment than the standard relativistic DFT values with 25% exact-exchange, and are also noticeably better than the relativistic PBE0 results obtained with 50% exact-exchange. Further improvement is achieved by adding rovibrational corrections, estimated using literature data. Published by AIP Publishing. [http://dx

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Section: Methodsmentioning

confidence: 99%

Indirect NMR spin–spin coupling constants in diatomic alkali halides

Jaszuński

Antušek

Demissie

et al. 2016

The Journal of Chemical Physics

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“…However, this may quickly become quite tedious, and an alternative approach is given by the use of real-time propagation methods. 168 Here the real-time response of the molecular system is followed in time, and information on, e.g., the absorption of the sample is obtained from this time-propagation. However, this approach is hampered by difficulties in separating the different-order responses, or differentorder molecular properties, and the calculation of transition energies and oscillator strengths for analysis.…”

Section: High-intensity Fieldsmentioning

confidence: 99%

“…It is to be noted that TDDFT is not the only DFT-based method applicable to core-excitation processes, nor is the linear response formalism the only way of formulating TDDFT -for the latter we have earlier discussed the possibility of real-time propagation, 33,168 and for the latter there exists state-specific methods based on ground state DFT (one of which is used in Paper [IV]). 13,15,16 A major concern here is that TDDFT lacks relaxation effects, as has been discussed in connection to the ethene example of Table 4.3, and one would thus assume that TDDFT is relatively useless for the simulation of X-ray absorption spectra.…”

Section: Treating Larger Systemsmentioning

confidence: 99%

“…For the former there exists also the possibility of explicitly propagating the molecular system in time, as has been developed for use for core excitations 33,167 and lately generalized to accommodate also relativistic effects by being applied in the four-component relativistic regime. 34,168 For the latter, a direct way of approximating transition energies are given with the ∆SCF approach, 169,170 in which the energetics of the ground state and explicit excited states are compared. Alternatively, it can be shown 15,16 that the transition energy is correct to second order if half an electron is excited to explicitly relaxed excited states, forming the so-called Slater transition state method.…”

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X-ray spectroscopies through damped linear response theory

Fransson¹

2016

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In order to reach a fundamental understanding of interactions between electromagnetic radiation and molecular materials, experimental measurements need to be supplemented with theoretical models and simulations. With the use of this combination, it is possible to characterize materials in terms of, e.g., chemical composition and molecular structure, as well as achieve time-resolution in studies of chemical reactions. This doctoral thesis focuses on the development and evaluation of theoretical methods with which, amongst others, X-ray absorption and X-ray emission spectroscopies can be interpreted and predicted. In X-ray absorption spectroscopy the photon energy is tuned such that core electrons are targeted and excited to either bound or continuum states, and X-ray emission spectroscopy measures the subsequent decay from such an excited state. These core excitations/de-excitations exhibit strong relaxation effects, making theoretical considerations of the processes particularly challenging. While the removal of a valence electron leaves the remaining electrons relatively unaffected, removing core electrons has a substantial effect on the other electrons due to the significant change in the screening of the nucleus. Additionally, the core-excited states are embedded in a manifold of valence-excited states that needs to be considered by some computationally feasible method. In this thesis, a damped formalism of linear response theory, which is a perturbative manner of considering the interactions of (weak) external or internal fields with molecular systems, has been utilized to investigate mainly the X-ray absorption spectra of small-to medium-sized molecular systems.Amongst the standard quantum chemical methods available, coupled cluster is perhaps the most accurate, with a well-defined, hierarchical manner of approaching the correct electronic wave function. Combined with response theory, it provides a reliable theoretical method in which relaxation effects are addressed by means of an accurate treatment of electron correlation. The first part of this thesis deals with the development and evaluation of such an approach, and it is shown that the relaxation effects can be addressed by the inclusion of double excitations in the coupled cluster manifold. However, these calculations are computationally very demanding, and in order to treat larger systems the performance of the coupled cluster approach has been compared to that of the less demanding method of timedensity dependent functional theory (TDDFT). Both methods have been used to v vi investigate the X-ray absorption spectrum of water, which has been extensively debated in the scientific community following a relatively recent hypothesis concerning the underlying structure of liquid water. Water exhibits a great number of anomalous properties that stand out from those of most compounds, and the importance of reaching a fundamental understanding of this substance cannot be overstated. It has been demonstrated that TDDFT yields excellent results for liq...

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“…To accomplish this, we extended a recent implementation of the PCM-Self-Consistent Field (SCF) scheme at the relativistic four-component DFT level of theory [76] to the Kramers-unrestricted regime and assessed the methodology in calculations of EPR gand A-tensors, as well as the temperature-dependent contribution to pNMR shifts. The implementation is done in the ReSpect [77] program package and utilizes the same modular strategy as exploited in the DIRAC implementation [76]: the PCM functionality is provided by an interface to the independently developed PCMSolver library [78].…”

Section: Introductionmentioning

confidence: 99%

Four-component relativistic density functional theory with the polarisable continuum model: application to EPR parameters and paramagnetic NMR shifts

et al. 2016

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The description of chemical phenomena in solution is as challenging as it is important for the accurate calculation of molecular properties. Here, we present the implementation of the polarizable continuum model (PCM) in the four-component Dirac-Kohn-Sham density functional theory framework, o↵ering a cost-e↵ective way to concurrently model solvent and relativistic e↵ects. The implementation is based on the matrix representation of the Dirac-Coulomb Hamiltonian in the basis of restricted kinetically balanced Gaussian-type functions, exploiting a non-collinear Kramers unrestricted formalism implemented in the program ReSpect, and the integral equation formalism of the PCM (IEF-PCM) available through the standalone library PCMSolver. Calculations of EPR parameters (g-tensors and hyperfine coupling A-tensors), as well as of the temperature-dependent contribution to paramagnetic NMR (pNMR) shifts, are presented to validate the model and to demonstrate the importance of taking both relativistic and solvent e↵ects into account for magnetic properties. As shown for selected Ru and Os complexes, the solvent shifts may amount to as much as 25% of the gas-phase values for g-tensor components and even more for pNMR shifts in some extreme cases.

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Excitation Energies from Real-Time Propagation of the Four-Component Dirac–Kohn–Sham Equation

Cited by 89 publications

References 71 publications

Indirect NMR spin–spin coupling constants in diatomic alkali halides

Indirect NMR spin–spin coupling constants in diatomic alkali halides

X-ray spectroscopies through damped linear response theory

Four-component relativistic density functional theory with the polarisable continuum model: application to EPR parameters and paramagnetic NMR shifts

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