scholarly journals Relaxation of ArH+ by collision with He: Isotopic effects

2019 ◽  
Vol 631 ◽  
pp. A86 ◽  
Author(s):  
Ricardo M. García-Vázquez ◽  
Maykel Márquez-Mijares ◽  
Jesús Rubayo-Soneira ◽  
Otoniel Denis-Alpizar
Keyword(s):  
Reproducing Kernel ◽  
Noble Gas ◽  
Reproducing Kernel Hilbert Space ◽  
Three Dimensional ◽  
Basis Set ◽  
Basis Sets ◽  
Rate Coefficients ◽  
Relaxation Rates ◽  
Rotational States ◽  
Isotopic Effects

Context. The study of noble gas compounds has gained renewed interest thanks to the recent detection of ArH+ in the interstellar medium (ISM). The analysis of physical-chemical conditions in the regions of the ISM where ArH+ is observed requires accurate collisional data of ArH+ with He, H2, electrons, and H. Aims. The main goals of this work are to compute the first three-dimensional potential energy surface (PES) to study the interaction of ArH+ with He, analyze the influence of the isotopic effects in the rate coefficients, and evaluate the rovibrational relaxation rates. Methods. Two ab initio grids of energy were computed at the coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) level of theory using the augmented correlation consistent polarized quadruple, and quintuple zeta basis sets (aug-cc-pVQZ, and aug-cc-pV5Z) and a grid at the complete basis set limit was determined. The analytical representation of the PES was performed using the reproducing kernel Hilbert space (RKHS). The dynamics of the system was studied using the close coupling method. Results. The differences in the rate coefficients for the isotopes 36ArH+, 38ArH+, and 40ArH+ in collision with He are negligible. However, the rotational rates for the collision of ArD+ with He cannot be estimated from those for ArH++He. Comparison with previous rates for the 36ArH++He collision showed discrepancies for ∣ Δj ∣ > 2, and in the case of high initial rotational states of 36ArH+ differences were found even for ∣ Δj ∣ = 1. The rates for transitions between different vibrational states were also examined. Finally, new sets of rotational rates for 36ArH++He and 36ArD++He are reported.

Relaxation of NO+ by collision with para-H2 (j = 0)

2020 ◽  
Vol 494 (1) ◽  
pp. 129-134
Author(s):  
L D Cabrera-González ◽  
D Páez-Hernández ◽  
O Denis-Alpizar
Keyword(s):  
Cross Sections ◽  
Reproducing Kernel ◽  
Reproducing Kernel Hilbert Space ◽  
Rate Coefficients ◽  
Local Thermal Equilibrium ◽  
Large Set ◽  
Close Coupling ◽  
Rotational States ◽  
Scaling Procedure ◽  
Collisional Rate Coefficients

ABSTRACT The first tentative detection of the nitrosylium ion (NO+) in the interstellar medium (ISM) was reported just a few years ago. The application of non-local thermal equilibrium models requires the knowledge of the collisional rate coefficients with the most common colliders in the ISM (e.g. He, H, H2, and e). The main goals of this paper are to study the collision of the NO+ molecule with para-H2 (j = 0) and report the rate coefficients for the lower rotational states of NO+. A large set of ab initio energies was computed at the CCSD(T)/aug-cc-pV5Z level of theory. A new potential energy surface averaged over the H2 orientations was then fitted using a reproducing kernel Hilbert space procedure. The state-to-state cross-sections of NO++para-H2 (j = 0) for the first 18 rotational levels were computed using the close-coupling method. The rotational rate coefficients of this system were compared with those for NO++He, and a different propensity rule was found. Furthermore, the hyperfine rate coefficients were also calculated using the infinite-order-sudden scaling procedure.

Inelastic scattering of interstellar silyl cyanide (SiH3CN) by helium atoms : cross-sections and rate coefficients for A- and E-SiH3CN

2021 ◽  
Vol 507 (4) ◽  
pp. 5264-5271
Author(s):  
Manel Naouai ◽  
Abdelhak Jrad ◽  
Ayda Badri ◽  
Faouzi Najar
Keyword(s):  
Inelastic Scattering ◽  
Total Energy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Explicitly Correlated ◽  
Correlation Consistent ◽  
Triple Excitation

ABSTRACT Rotational inelastic scattering of silyl cyanide (SiH3CN) molecule with helium (He) atoms is investigated. Three-dimensional potential energy surface (3D-PES) for the SiH3CN–He interacting system is carried out. The ab initio 3D-PES is computed using explicitly correlated coupled cluster approach with single, double, and perturbative triple excitation CCSD(T)-F12a connected to augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. A global minimum at (R = 6.35 bohr; θ = 90○; ϕ = 60○) with a well depth of 52.99 cm−1 is pointed out. Inelastic rotational cross-sections are emphasized for the 22 first rotational levels for total energy up to 500 cm−1 via close coupling (CC) approach in the case of A-SiH3CN and for the 24 first rotational levels for total energy up to 100 cm−1 via CC and from 100 to 500 cm−1 via coupled states (CS) in the case of E-SiH3CN. Rate coefficients are derived for temperature until 80 K for both A- and E-SiH3CN–He systems. Propensity rules are obtained for |ΔJ| = 2 processes with broken parity for A-SiH3CN and for |ΔJ| = 2 processes with |ΔK| = 0 and unbroken parity for E-SiH3CN.

scholarly journals Reproducing kernel approach for numerical solutions of fuzzy fractional initial value problems under the Mittag-Leffler kernel differential operator

2021 ◽  
Author(s):  
omar abu arqub ◽  
Jagdev Singh ◽  
Banan Maayah ◽  
Mohammed Alhodaly
Keyword(s):  
Reproducing Kernel ◽  
Differential Operators ◽  
Numerical Solutions ◽  
Reproducing Kernel Hilbert Space ◽  
Research Work ◽  
Three Dimensional ◽  
Characterization Theorem ◽  
Space Technique ◽  
Kernel Approach ◽  
Reproducing Kernel Theory

In this research study, fuzzy fractional differential equations in presence of the Atangana-Baleanu-Caputo differential operators are analytically and numerically treated using extended reproducing Kernel Hilbert space technique. With the utilization of a fuzzy strongly generalized differentiability form, a new fuzzy characterization theorem beside two fuzzy fractional solutions is constructed and computed. To besetment the attitude of fuzzy fractional numerical solutions; analysis of convergence and conduct of error beyond the reproducing kernel theory are explored and debated. In this tendency, three computational algorithms and modern trends in terms of analytic and numerical solutions are propagated. Meanwhile, the dynamical characteristics and mechanical features of these fuzzy fractional solutions are demonstrated and studied during two applications via three-dimensional graphs and tabulated numerical values. In the end, highlights and future suggested research work are eluded.

scholarly journals Rotational relaxation of HCO+ and DCO+ by collision with H2

2020 ◽  
Vol 497 (4) ◽  
pp. 4276-4281 ◽  
Author(s):  
Otoniel Denis-Alpizar ◽  
Thierry Stoecklin ◽  
Anne Dutrey ◽  
Stéphane Guilloteau
Keyword(s):  
Cross Sections ◽  
Rate Coefficients ◽  
Local Thermal Equilibrium ◽  
Rotational Relaxation ◽  
Close Coupling ◽  
Excitation Rate ◽  
Rotational States ◽  
Non Local ◽  
The Difference ◽  
Isotopic Effects

ABSTRACT The HCO+ and DCO+ molecules are commonly used as tracers in the interstellar medium. Therefore, accurate rotational rate coefficients of these systems with He and H2 are crucial in non-local thermal equilibrium models. We determine in this work the rotational de-excitation rate coefficients of HCO+ in collision with both para- and ortho-H2, and also analyse the isotopic effects by studying the case of DCO+. A new four-dimensional potential energy surface from ab initio calculations was developed for the HCO+–H2 system, and adapted to the DCO+–H2 case. These surfaces are then employed in close-coupling calculations to determine the rotational de-excitation cross-sections and rate coefficients for the lower rotational states of HCO+ and DCO+. The new rate coefficients for HCO+ + para-H2 were compared with the available data, and a set of rate coefficients for HCO+ + ortho-H2 is also reported. The difference between the collision rates with ortho- and para-H2 is found to be small. These calculations confirm that the use of the rate coefficients for HCO+ + para-H2 for estimating those for HCO+ + ortho-H2 as well as for DCO+ + para-H2 is a good approximation.

On the nature of the bonding in X-Be-O molecules (X = He, Ne, Ar)

1988 ◽  
Vol 53 (10) ◽  
pp. 2230-2238 ◽  
Author(s):  
Pavel Hobza ◽  
Paul von Ragué Schleyer
Keyword(s):  
Charge Transfer ◽  
Noble Gas ◽  
Basis Set ◽  
Basis Sets ◽  
Reverse Direction ◽  
Basis Set Superposition Error ◽  
Back Donation ◽  
Induction Energy ◽  
Extended Basis ◽  
Split Valence

The noble gas complexes, HeBeO, NeBeO, and ArBeO, discovered calculationally by Koch and Frenking, were reexamined at various theoretical levels. The results depended strongly on the size of the basis set but were insensitive to electron correlation corrections. The MP2 association energies of BeO with the noble gases, obtained with extended basis sets, were 4·80, 4·76, and 10·12 kcal/mol, respectively. The surprising stability of HeBeO (compared to NeBeO) is due to greater charge-transfer from He to BeO (donation) as well as to charge-transfer in the reverse direction (back donation). This compensates for the larger induction energy due to the greater polarizability of neon. The basis set superposition error is very large with split-valence basis sets; improvement of s and p function descriptions strongly reduces but does not completely eliminate this error.

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

DFT Benchmark Study of the O--O Bond Dissociation Energy in Peroxides Validated with High-Level Ab-Initio Calculations

2019 ◽  
Author(s):  
Danilo Carmona ◽  
Pablo Jaque ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Reference Value ◽  
Basis Set ◽  
Basis Sets ◽  
Mean Deviation ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
The Mean ◽  
Experimental Values ◽  
High Level ◽  
Almost All

<div><div><div><p>Peroxides play a central role in many chemical and biological pro- cesses such as the Fenton reaction. The relevance of these compounds lies in the low stability of the O–O bond which upon dissociation results in radical species able to initiate various chemical or biological processes. In this work, a set of 64 DFT functional-basis set combinations has been validated in terms of their capability to describe bond dissociation energies (BDE) for the O–O bond in a database of 14 ROOH peroxides for which experimental values ofBDE are available. Moreover, the electronic contributions to the BDE were obtained for four of the peroxides and the anion H2O2− at the CBS limit at CCSD(T) level with Dunning’s basis sets up to triple–ζ quality provid- ing a reference value for the hydrogen peroxide anion as a model. Almost all the functionals considered here yielded mean absolute deviations around 5.0 kcal mol−1. The smallest values were observed for the ωB97 family and the Minnesota M11 functional with a marked basis set dependence. Despite the mean deviation, order relations among BDE experimental values of peroxides were also considered. The ωB97 family was able to reproduce the relations correctly whereas other functionals presented a marked dependence on the chemical nature of the R group. Interestingly, M11 functional did not show a very good agreement with the established order despite its good performance in the mean error. The obtained results support the use of similar validation strategies for proper prediction of BDE or other molecular properties by DF Tmethods in subsequent related studies.</p></div></div></div>

Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

2019 ◽  
Author(s):  
Kamal Batra ◽  
Stefan Zahn ◽  
Thomas Heine
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Absolute Error ◽  
Time Dependent ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
Framework Materials ◽  
Dependent Density

<p>We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV). </p>

Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
Author(s):  
Sanchit Chhabra ◽  
T J Dhilip Kumar
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Cross Sections ◽  
Energy Surface ◽  
Molecular Ions ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

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