Taha Selim, PhD

Accurate theoretical models and powerful simulations are increasingly crucial for innovation in vital sectors like healthcare, electric vehicles, new materials, and chemistry. However, classical computers face significant challenges in scalability and accuracy, as exemplified by the computationally intensive simulation of induced rotational-vibrational transitions in CO2-He collisions—a key focus of my PhD research at Radboud University.

Quantum AI, a nascent field merging quantum… Meer weergeven

Accurate theoretical models and powerful simulations are increasingly crucial for innovation in vital sectors like healthcare, electric vehicles, new materials, and chemistry. However, classical computers face significant challenges in scalability and accuracy, as exemplified by the computationally intensive simulation of induced rotational-vibrational transitions in CO2-He collisions—a key focus of my PhD research at Radboud University.

Quantum AI, a nascent field merging quantum physics and artificial intelligence, offers a potential solution. It promises AI models capable of learning the underlying physics of systems, large and small, and tackling currently intractable problems. Realizing this potential requires deep expertise in quantum physics, quantum computing, and machine learning, along with the development of models trainable on quantum data and predictive of quantum system behavior. Furthermore, a robust community of researchers, developers, and practitioners is essential for sharing knowledge, tools, and best practices.

This talk will explore:

the complexities of chemistry simulations and the need for accurate theoretical models;
the expected performance from quantum computers;
the current state of Quantum AI research;
illustrative use cases in chemistry simulations;
the emerging Quantum AI community and ecosystem developed by Quantum AI Lab/iQafé in collaboration with the Bibliotheca Alexandrina;
and the vital role of community activities, such as hackathons, in fostering a thriving Quantum AI ecosystem. Minder weergeven

Modeling environments that are not in local thermal equilibrium, such as protoplanetary disks or planetary atmospheres, with molecular spectroscopic data requires knowledge of the rates of rovibrationally inelastic molecular collisions. Here, we present rate coefficients for temperatures up to 500 K for CO2-He collisions in which CO2 is (de)excited in the bend mode. They are obtained from numerically exact coupled-channel (CC) calculations as well as from calculations with the less demanding… Meer weergeven

Modeling environments that are not in local thermal equilibrium, such as protoplanetary disks or planetary atmospheres, with molecular spectroscopic data requires knowledge of the rates of rovibrationally inelastic molecular collisions. Here, we present rate coefficients for temperatures up to 500 K for CO2-He collisions in which CO2 is (de)excited in the bend mode. They are obtained from numerically exact coupled-channel (CC) calculations as well as from calculations with the less demanding coupled-states approximation (CSA) and the vibrational close-coupling rotational infinite-order sudden (VCC-IOS) method. All of the calculations are based on a new accurate ab initio four-dimensional CO2-He potential surface including the CO2 bend mode. We find that the rovibrationally inelastic collision cross sections and rate coefficients from the CSA and VCC-IOS calculations agree mostly to within 50% with the CC results at the rotational state-to-state level and to within 20% for the overall vibrational quenching rates except for temperatures below 50 K where resonances provide a substantial contribution. Our CC quenching rates agree with the most recent experimental data within the error bars. We also compared our results with data from Clary et al. calculated in the 1980's with the CSA and VCC-IOS methods and a simple atom-atom model potential based on ab initio Hartree-Fock calculations and found that their cross sections agree fairly well with ours for collision energies above 500 cm-1, but that the inclusion of long range attractive dispersion interactions is crucial to obtain reliable cross sections at lower energies and rate coefficients at lower temperatures.

*Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO).Dutch Astrochemistry Network DAN-II. Minder weergeven

Modeling environments that are not in local thermal equilibrium, such as protoplanetary disks or planetary atmospheres, with molecular spectroscopic data from space telescopes requires knowledge of the rate coefficients of rovibrationally inelastic molecular collisions. Here, we present such rate coefficients in a temperature range from 10 to 500 K for collisions of CO2 with He atoms in which CO2 is (de)excited in the bend mode. They are obtained from numerically exact coupled-channel (CC)… Meer weergeven

Modeling environments that are not in local thermal equilibrium, such as protoplanetary disks or planetary atmospheres, with molecular spectroscopic data from space telescopes requires knowledge of the rate coefficients of rovibrationally inelastic molecular collisions. Here, we present such rate coefficients in a temperature range from 10 to 500 K for collisions of CO2 with He atoms in which CO2 is (de)excited in the bend mode. They are obtained from numerically exact coupled-channel (CC) calculations as well as from calculations with the less demanding coupled-states approximation (CSA) and the vibrational close-coupling rotational infinite-order sudden (VCC-IOS) method. All of the calculations are based on a newly calculated accurate ab initio four-dimensional CO2–He potential surface including the CO2 bend (ν2) mode. We find that the rovibrationally inelastic collision cross sections and rate coefficients from the CSA and VCC-IOS calculations agree to within 50% with the CC results at the rotational state-to-state level, except for the smaller ones and in the low energy resonance region, and to within 20% for the overall vibrational quenching rates except for temperatures below 50 K where resonances provide a substantial contribution. Our CC quenching rates agree with the most recent experimental data within the error bars. We also compared our results with data from Clary et al. calculated in the 1980s with the CSA [A. J. Banks and D. C. Clary, J. Chem. Phys. 86, 802 (1987)] and VCC-IOS [D. C. Clary, J. Chem. Phys. 78, 4915 (1983)] methods and a simple atom-atom model potential based on ab initio Hartree–Fock calculations and found that their cross sections agree fairly well with ours for collision energies above 500 cm−1, but that the inclusion of long range attractive dispersion interactions is crucial to obtain reliable cross sections at lower energies and rate coefficients at lower temperatures. Minder weergeven

#quantum #mechanical methods provide accurate #simulations for the molecular dynamical processes involving quantum-mechanical behavior such as molecular interactions and behavior during molecular collisions.

However, such methods are computationally demanding and expensive for large systems; computations involving molecules with a large number of states; for example rotational and vibrational states.

--> Hence, we reduce the CPU time and make such calculations… Meer weergeven

#quantum #mechanical methods provide accurate #simulations for the molecular dynamical processes involving quantum-mechanical behavior such as molecular interactions and behavior during molecular collisions.

However, such methods are computationally demanding and expensive for large systems; computations involving molecules with a large number of states; for example rotational and vibrational states.

--> Hence, we reduce the CPU time and make such calculations affordable.

arXiv: https://arxiv.org/abs/2206.04470

--> In our paper, we present various approximate, but more efficient methods, to calculate the collision rates and highlight the quantum scattering dynamics in molecular collisions. Minder weergeven

Modeling protoplanetary disks and other interstellar media that are not in local thermal equilibrium require the knowledge of rovibrational transition rate coefficients of molecules in collision with helium and hydrogen. We present a computational method based on the numerically exact coupled-channel (CC) method for rotational transitions and a multi-channel distorted-wave Born approximation (MC-DWBA) for vibrational transitions to calculate state-to-state rate coefficients. We apply this… Meer weergeven

Modeling protoplanetary disks and other interstellar media that are not in local thermal equilibrium require the knowledge of rovibrational transition rate coefficients of molecules in collision with helium and hydrogen. We present a computational method based on the numerically exact coupled-channel (CC) method for rotational transitions and a multi-channel distorted-wave Born approximation (MC-DWBA) for vibrational transitions to calculate state-to-state rate coefficients. We apply this method to the astrophysically important case of CO2–He collisions, using newly computed ab initio three-dimensional potential energy surfaces for CO2–He with CO2 distorted along the symmetric and asymmetric stretch (ν1 and ν3) coordinates. It is shown that the MC-DWBA method is almost as accurate as full CC calculations, but more efficient. We also made computations with the more approximate vibrational coupled-channel rotational infinite-order sudden method but found that this method strongly underestimates the vibrationally inelastic collision cross sections and rate coefficients for both CO2 modes considered. Minder weergeven