M<scp>O</scp>V<scp>I</scp>P<scp>AC</scp>: Vibrational spectroscopy with a robust meta‐program for massively parallel standard and inverse calculations

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We describe the calculation of Raman spectra for periodic systems via ab initio molecular dynamics (AIMD) utilizing the Gaussian and plane wave method in the program package CP2K. The electric-dipole–electric-dipole polarizability tensor has been implemented for an arbitrary shape of the simulation cell. In addition, a computationally efficient approach for its decomposition into local contributions is presented. As an example for the application of computational Raman spectroscopy to liquids, the Raman spectra of S-methyloxirane in the liquid phase have been calculated together with Raman spectra obtained from static calculations employing the double-harmonic approximation. The comparison to experimental data illustrates that a very good agreement between experiment and simulated spectra can be obtained employing AIMD, which takes into account anharmonicities and dynamical effects at ambient conditions.

Section: Computational Methodologymentioning

confidence: 99%

Raman spectra from ab initio molecular dynamics and its application to liquid S-methyloxirane

Luber

Iannuzzi

Hutter

2014

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“…44 We start from the optimized ground-state structure and perform an excited-state calculation including the calculation of vertical electronic excitation energies, oscillator strengths, and excited-state gradients (only singlet excited states are considered here). In the present work, we employed the egrad 45, 46 module from the TURBOMOLE program package, 47 for the latter purpose.…”

Section: Implementation and Computational Detailsmentioning

confidence: 99%

“…48 The corresponding frequency analysis is performed with the program SNF 12 from the MoViPac suite. 44 For the calculation of the integral in Eq.…”

Section: Implementation and Computational Detailsmentioning

confidence: 99%

“…For this purpose, we have included the relevant routines of the ABSORBER program into the general-purpose mode-tracking program AKIRA. 13,44 If the spectrum is not yet converged, an approximate normal mode is selected for further refinement. Here, we select that particular normal-mode approximation which has the largest displacement i and which is not yet converged according to its residual vector.…”

Section: Implementation and Computational Detailsmentioning

confidence: 99%

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Vibronic-structure tracking: A shortcut for vibrationally resolved UV/Vis-spectra calculations

Barton

König

Neugebauer

2014

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The vibrational coarse structure and the band shapes of electronic absorption spectra are often dominated by just a few molecular vibrations. By contrast, the simulation of the vibronic structure even in the simplest theoretical models usually requires the calculation of the entire set of normal modes of vibration. Here, we exploit the idea of the mode-tracking protocol [M. Reiher and J. Neugebauer, J. Chem. Phys. 118, 1634 (2003)] in order to directly target and selectively calculate those normal modes which have the largest effect on the vibronic band shape for a certain electronic excitation. This is achieved by defining a criterion for the importance of a normal mode to the vibrational progressions in the absorption band within the so-called "independent mode, displaced harmonic oscillator" (IMDHO) model. We use this approach for a vibronic-structure investigation for several small test molecules as well as for a comparison of the vibronic absorption spectra of a truncated chlorophyll a model and the full chlorophyll a molecule. We show that the method allows to go beyond the often-used strategy to simulate absorption spectra based on broadened vertical excitation peaks with just a minimum of computational effort, which in case of chlorophyll a corresponds to about 10% of the cost for a full simulation within the IMDHO approach.

“…1, 2 In contrast to static calculations, [3][4][5][6][7][8][9][10][11][12][13] this approach naturally takes into account the dynamics of the studied system at ambient conditions. In order to be able to discriminate the contributions of different components in the system, it is necessary to evaluate not only the total electric dipole moment of the system but also local electric dipole moments.…”

Section: Introductionmentioning

confidence: 99%

Local electric dipole moments for periodic systems via density functional theory embedding

Luber

2014

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We describe a novel approach for the calculation of local electric dipole moments for periodic systems. Since the position operator is ill-defined in periodic systems, maximally localized Wannier functions based on the Berry-phase approach are usually employed for the evaluation of local contributions to the total electric dipole moment of the system. We propose an alternative approach: within a subsystemdensity functional theory based embedding scheme, subset electric dipole moments are derived without any additional localization procedure, both for hybrid and non-hybrid exchange-correlation functionals. This opens the way to a computationally efficient evaluation of local electric dipole moments in (molecular) periodic systems as well as their rigorous splitting into atomic electric dipole moments. As examples, Infrared spectra of liquid ethylene carbonate and dimethyl carbonate are presented, which are commonly employed as solvents in Lithium ion batteries. We describe a novel approach for the calculation of local electric dipole moments for periodic systems. Since the position operator is ill-defined in periodic systems, maximally localized Wannier functions based on the Berry-phase approach are usually employed for the evaluation of local contributions to the total electric dipole moment of the system. We propose an alternative approach: within a subsystem-density functional theory based embedding scheme, subset electric dipole moments are derived without any additional localization procedure, both for hybrid and non-hybrid exchangecorrelation functionals. This opens the way to a computationally efficient evaluation of local electric dipole moments in (molecular) periodic systems as well as their rigorous splitting into atomic electric dipole moments. As examples, Infrared spectra of liquid ethylene carbonate and dimethyl carbonate are presented, which are commonly employed as solvents in Lithium ion batteries. © 2014 AIP Publishing LLC. [http://dx