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To alleviate the computational cost associated with on-the-fly ab initio semiclassical calculations of molecular spectra, we propose the single-Hessian thawed Gaussian approximation, in which the Hessian of the potential energy at all…

Chemical Physics · Physics 2024-09-26 Tomislav Begušić , Manuel Cordova , Jiří Vaníček

Simulating vibrationally resolved electronic spectra of anharmonic systems, especially those involving double-well potential energy surfaces, often requires expensive quantum dynamics methods. Here, we explore the applicability and…

Chemical Physics · Physics 2022-05-12 Tomislav Begušić , Enrico Tapavicza , Jiří Vaníček

To compute and analyze vibrationally resolved electronic spectra at zero temperature, we have recently implemented the on-the-fly ab initio extended thawed Gaussian approximation [A. Patoz et al., J. Phys. Chem. Lett. 9, 2367 (2018)], which…

Chemical Physics · Physics 2024-09-26 Tomislav Begušić , Jiří Vaníček

Evaluation of symmetry-forbidden or weakly-allowed vibronic spectra requires treating the transition dipole moment beyond the Condon approximation. To include vibronic spectral features not captured in the global harmonic models, we have…

Chemical Physics · Physics 2019-01-17 Tomislav Begušić , Aurélien Patoz , Miroslav Šulc , Jiří Vaníček

We present a methodology for computing vibrationally and time-resolved pump-probe spectra, which takes into account all vibrational degrees of freedom and is based on the combination of the thawed Gaussian approximation with on-the-fly ab…

Chemical Physics · Physics 2019-01-31 Tomislav Begušić , Julien Roulet , Jiří Vaníček

Ab initio computation of two-dimensional electronic spectra is an expanding field, whose goal is improving upon simple, few-dimensional models often employed to explain experiments. Here, we propose an accurate and computationally…

Chemical Physics · Physics 2024-09-26 Tomislav Begušić , Jiří Vaníček

To evaluate vibronic spectra beyond the Condon approximation, we extend the on-the-fly ab initio thawed Gaussian approximation by considering the Herzberg-Teller contribution due to the dependence of the electronic transition dipole moment…

Chemical Physics · Physics 2018-12-12 Aurélien Patoz , Tomislav Begušić , Jiří Vaníček

We describe a new approach based on semiclassical molecular dynamics that allows to simulate infrared absorption or emission spectra of molecular systems with inclusion of anharmonic intensities. This is achieved from semiclassical power…

Chemical Physics · Physics 2018-11-12 Marco Micciarelli , Riccardo Conte , Jaime Suarez , Michele Ceotto

We use the so-called eikonal approximation, recently introduced in the context of cosmological perturbation theory, to compute power spectra for multi-component fluids. We demonstrate that, at any given order in standard perturbation…

Cosmology and Nongalactic Astrophysics · Physics 2013-10-10 Francis Bernardeau , Nicolas Van de Rijt , Filippo Vernizzi

We introduce an improved semiclassical dynamics approach to quantum vibrational spectroscopy. In this method, a harmonic-based phase space sampling is preliminarily driven toward non-harmonic quantization by slowly switching on the actual…

Chemical Physics · Physics 2019-12-09 Riccardo Conte , Lorenzo Parma , Chiara Aieta , Alessandro Rognoni , Michele Ceotto

The theoretical prediction of the rates of nonradiative processes in molecules is fundamental to assess their emissive properties. In this context, global harmonic models have been widely used to simulate vibronic spectra as well as…

Chemical Physics · Physics 2023-02-01 Michael Wenzel , Roland Mitric

We consider the effects of electron-hole interaction, 2D confinement and applied electric field on direct allowed transitions in III-V semiconductors, with InGaAs as a study case. Instead of Coulomb interaction, we use Gaussian potential.…

Computational Physics · Physics 2021-01-18 Yuriy D. Sibirmovsky , Ivan S. Vasil'evskii , Nikolay I. Kargin

A general and rigorous methodology to compute the quantum equilibrium isotope effect is described. Unlike standard approaches, ours does not assume separability of rotational and vibrational motions and does not make the harmonic…

Chemical Physics · Physics 2015-05-13 Tomas Zimmermann , Jiri Vanicek

A method for performing variable-width (thawed) Gaussian wavepacket (GWP) variational dynamics on machine-learned potentials is presented. Instead of fitting the potential energy surface (PES), the anharmonic correction to the global…

Chemical Physics · Physics 2024-12-17 Rami Gherib , Ilya G. Ryabinkin , Scott N. Genin

The electronic Schr\"odinger equation describes the motion of N electrons under Coulomb interaction forces in a field of clamped nuclei. The solutions of this equation, the electronic wavefunctions, depend on 3N variables, three spatial…

Numerical Analysis · Mathematics 2017-01-16 Stephan Scholz , Harry Yserentant

Several thermodynamic properties of ice Ih, II, and III are studied by a quasi-harmonic approximation and compared to results of quantum path integral and classical simulations. This approximation allows to obtain thermodynamic information…

Chemical Physics · Physics 2012-09-24 R. Ramirez , N. Neuerburg , M. -V. Fernandez-Serra , C. P. Herrero

Despite the widespread use of silicon in modern technology, its peculiar thermal expansion is not well-understood. Adapting harmonic phonons to the specific volume at temperature, the quasiharmonic approximation, has become accepted for…

Spectral, optical and transport properties of an anisotropic three-dimensional Holstein model are studied within the adiabatic approximation. The parameter regime is appropriate for organic semiconductors used in single crystal based field…

Strongly Correlated Electrons · Physics 2015-05-27 C. A. Perroni , A. Nocera , V. Marigliano Ramaglia , V. Cataudella

Accurate simulation of the non-adiabatic dynamics of molecules in excited electronic states is key to understanding molecular photo-physical processes. Here we present a novel method, based on a semiclassical approximation, that is as…

Chemical Physics · Physics 2016-05-24 Alexander White , Sergei Tretiak , Dmitry Mozyrsky

With increasing energy the diamagnetic hydrogen atom undergoes a transition from regular to chaotic classical dynamics, and the closed orbits pass through various cascades of bifurcations. Closed orbit theory allows for the semiclassical…

Chaotic Dynamics · Physics 2007-05-23 T. Fabcic , J. Main , T. Bartsch , G. Wunner
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