Publications by Jiri Vanicek | EPFL Graph Search

Ehrenfest dynamics accelerated with SPEED

Mixed quantum-classical methods, such as surface hopping and Ehrenfest dynamics, have proven useful for describing molecular processes involving multiple electronic states. These methods require propagating many independent trajectories, which is computati ...

AIP Publishing2025

Can increasing the size and flexibility of a molecule reduce decoherence and prolong charge migration?

Jiri Vanicek, Alan Scheidegger

Coherent superposition of electronic states, created by ionizing a molecule, can initiate ultrafast dynamics of the electron density. Correlation between nuclear and electron motions, however, typically dissipates the electronic coherence in only a few fem ...

NAS2025

On-the-fly ab initio Hagedorn wave-packet dynamics: Single vibronic level fluorescence spectra of difluorocarbene

Jiri Vanicek, Zhan Tong Zhang, Máté Visegrádi

Hagedorn wave packets have been used to compute single vibronic level (SVL) spectra efficiently in model harmonic potentials. To make the Hagedorn approach practical for realistic polyatomic molecules with anharmonicity, here we combine local harmonic Hage ...

American Physical Society (APS)2025

On Hagedorn wavepackets associated with different Gaussians

Jiri Vanicek, Zhan Tong Zhang

Hagedorn functions are carefully constructed generalizations of Hermite functions to the setting of many-dimensional squeezed and coupled harmonic systems. Wavepackets formed by superpositions of Hagedorn functions have been successfully used to solve the ...

IOP Publishing2025

Finite-temperature vibronic spectra from the split-operator coherence thermofield dynamics

Jiri Vanicek, Zhan Tong Zhang

We present a numerically exact approach for evaluating vibrationally resolved electronic spectra at finite temperatures using the coherence thermofield dynamics. In this method, which avoids implementing an algorithm for solving the von Neumann equation fo ...

2024

Single vibronic level fluorescence spectra from Hagedorn wavepacket dynamics

Jiri Vanicek, Zhan Tong Zhang

In single vibronic level (SVL) fluorescence experiments, the electronically excited initial state is also excited in one or several vibrational modes. Because computing such spectra by evaluating all contributing Franck–Condon factors becomes impractical ( ...

AIP Publishing2024

Isotope Effects on the Electronic Spectra of Ammonia from Ab Initio Semiclassical Dynamics

Jiri Vanicek, Yannick Calvino Alonso, Eriks Kletnieks

Despite its simplicity, the single-trajectory thawed Gaussian approximation has proven useful for calculating the vibrationally resolved electronic spectra of molecules with weakly anharmonic potential energy surfaces. Here, we show that the thawed Gaussia ...

2023

High-order geometric integrators for the variational Gaussian approximation

Jiri Vanicek, Roya Moghaddasi Fereidani

Among the single-trajectory Gaussian-based methods for solving the time-dependent Schrödinger equation, the variational Gaussian approximation is the most accurate one. In contrast to Heller’s original thawed Gaussian approximation, it is symplectic, conse ...

2023

Family of Gaussian wavepacket dynamics methods from the perspective of a nonlinear Schrodinger equation

Jiri Vanicek

Many approximate solutions of the time-dependent Schrodinger equation can be formulated as exact solutions of a nonlinear Schrodinger equation with an effective Hamiltonian operator depending on the state of the system. We show that Heller's thawed Gaussia ...

2023

Sampling strategies for the Herman-Kluk propagator of the wavefunction

Jiri Vanicek

When the semiclassical Herman-Kluk propagator is used for evaluating quantum-mechanical observables or time-correlation functions, the initial conditions for the guiding trajectories are typically sampled from the Husimi density. Here, we employ this propa ...

2023

How to Find Molecules with Long-lasting Charge Migration?

Jiri Vanicek, Nikolay Golubev, Alan Scheidegger

Under certain conditions, the ionization of a molecule may create a superposition of electronic states, leading to ultrafast electron dynamics. If controlled, this motion could be used in attochemistry applications, but it has been shown that the decoheren ...

SWISS CHEMICAL SOC2023

Efficient Semiclassical Evaluation of Electronic Coherences in Polyatomic Molecules

Jiri Vanicek, Nikolay Golubev

Exposing a molecule to an intense light pulse can create a nonstationary quantum state, thus launching correlated dynamics of electrons and nuclei. Although much had been achieved in the understanding of fundamental physics behind the electron-nuclear inte ...

SWISS CHEMICAL SOC2022

Search for long-lasting electronic coherence using on-the-fly ab initio semiclassical dynamics

Jiri Vanicek, Nikolay Golubev, Alan Scheidegger

Using a combination of high-level ab initio electronic structure methods with efficient on-the-fly semiclassical evaluation of nuclear dynamics, we performed a massive scan of small polyatomic molecules searching for a long-lasting oscillatory dynamics of ...

AIP Publishing2022

Applicability of the Thawed Gaussian Wavepacket Dynamics to the Calculation of Vibronic Spectra of Molecules with Double-Well Potential Energy Surfaces br

Jiri Vanicek, Tomislav Begusic

Simulating vibrationally resolved electronic spectra of anharmonic systems, especially those involving double-wellpotential energy surfaces, often requires expensive quantumdynamics methods. Here, we explore the applicability andlimitations of the recently ...

AMER CHEMICAL SOC2022

Time-reversible and norm-conserving high-order integrators for the nonlinear time-dependent Schrödinger equation: Application to local control theory

Jiri Vanicek, Julien Roulet

The explicit split-operator algorithm has been extensively used for solving not only linear but also nonlinear time-dependent Schrödinger equations. When applied to the nonlinear Gross–Pitaevskii equation, the method remains time-reversible, norm-conservin ...

2021

How important are the residual nonadiabatic couplings for an accurate simulation of nonadiabatic quantum dynamics in a quasidiabatic representation?

Jiri Vanicek, Seonghoon Choi

Diabatization of the molecular Hamiltonian is a standard approach to remove the singularities of nonadiabatic couplings at conical intersections of adiabatic potential energy surfaces. In general, it is impossible to eliminate the nonadiabatic couplings en ...

2021

Efficient Semiclassical Dynamics for Vibronic Spectroscopy beyond Harmonic, Condon, and Zero-Temperature Approximations

Jiri Vanicek, Tomislav Begusic

Understanding light-induced processes in biological and human-made molecular systems is one of the main goals of physical chemistry. It has been known for years that the photoinduced dynamics of atomic nuclei can be studied by looking at the vibrational su ...

2021

An implicit split-operator algorithm for the nonlinear time-dependent Schrödinger equation

Jiri Vanicek, Julien Roulet

The explicit split-operator algorithm is often used for solving the linear and nonlinear time-dependent Schrödinger equations. However, when applied to certain nonlinear time-dependent Schrödinger equations, this algorithm loses time reversibility and seco ...

AIP Publishing2021

Core-Valence Attosecond Transient Absorption Spectroscopy of Polyatomic Molecules

Jiri Vanicek, Nikolay Golubev

Tracing ultrafast processes induced by interaction of light with matter is often very challenging. In molecular systems, the initially created electronic coherence becomes damped by the slow nuclear rearrangement on a femtosecond timescale which makes real ...

2021

High-order geometric integrators for representation-free Ehrenfest dynamics

Jiri Vanicek, Seonghoon Choi

Ehrenfest dynamics is a useful approximation for ab initio mixed quantum-classical molecular dynamics that can treat electronically nonadiabatic effects. Although a severe approximation to the exact solution of the molecular time-dependent Schrödinger equa ...

2021