Riyadh Corporation of Technology

Riyadh, Saudi Arabia

Riyadh Corporation of Technology

Riyadh, Saudi Arabia
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Yazidi O.,Tunis el Manar University | Ben Abdallah D.,Tunis el Manar University | Ben Abdallah D.,Riyadh Corporation of Technology | Lique F.,CNRS Laboratory of Waves and Complex Media | Lique F.,French National Center for Scientific Research
Monthly Notices of the Royal Astronomical Society | Year: 2014

Rotational excitation of the interstellar HCO+ by para-H2(j = 0) is investigated. The scattering calculations are based on a new potential energy surface (PES) for the HCO+-H2 van der Waals complex averaged over H2 orientations and considering both molecules as rigid rotors. The new ab initio PES was obtained from electronic structure calculations using a single and double excitation coupled cluster method with perturbative contributions from connected triple excitations [CCSD(T)]. The five atoms were described using the augmented correlation-consistent triple zeta basis set. For a better description of the van der Waals interaction, bond functions were placed approximately at mid-distance between the HCO+ and H2 centres of mass. Inelastic cross sections between rotational levels up to rotational momentum j = 20 were computed using a close coupling approach. Rate coefficients for temperatures ranging from 10 to 500 K were computed. The new rate coefficients were compared with previous results obtained for the HCO+ cation. Differences were found. We expect that the new rate coefficients will help to analyse present and future observations of this key ion for the interstellar chemistry. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Ajili Y.,University Paris Est Creteil | Ben Abdallah D.,Riyadh Corporation of Technology | Mogren Al-Mogren M.,King Saud University | Lique F.,CNRS Laboratory of Waves and Complex Media | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2016

The intermonomer three-dimensional potential-energy surface (3D PES) of the thiazyl-hydride-helium (HSN-He) weakly bound molecular system is generated using the explicitly correlated coupled-cluster method with single, double, and perturbative triple excitations. The 3D PES is mapped in Jacobi coordinates. This potential-energy surface shows a unique potential well at planar configurations. The depth of this potential is 74.4cm-1. This 3D PES is incorporated into a close-coupling and coupled-states quantum dynamical treatment of nuclear motions to deduce the rotational (de-)excitation of HSN by He for energies up to 1400cm-1. After averaging over a Maxwell-Boltzmann distribution, the collisional rate coefficients are derived for temperatures ranging from 5 to 200 K. These data are essential for the identification of HSN molecules in astrophysical media. A comparison between thionitrosyl-hydride - He and HSN-He is performed. © 2016 American Physical Society.


Ajili Y.,University Paris Est Creteil | Ben Abdallah D.,Riyadh Corporation of Technology | Mogren Al-Mogren M.,King Saud University | Francisco J.S.,Purdue University | Hochlaf M.,University Paris Est Creteil
Monthly Notices of the Royal Astronomical Society | Year: 2016

Three-dimensional potential energy surface (3D-PES) of the HNS-He interacting system in Jacobi coordinates is mapped using high-level ab initio theory. These computations are performed at the explicitly correlated coupled cluster method with single, double and perturbative triple excitations (CCSD(T)-F12) in conjunction with the augmented correlation-consistent aug-cc-pVTZ basis set. The 3D-PES is incorporated into quantum dynamical computations to treat the nuclear motions, where HNS is considered as a rigid rotator colliding with He. Cross-sections for transitions among the first twenty nine rotational levels of HNS (up to jKaKc = 92,8) are calculated using the quantum exact close-coupling method for total energies <1000 cm-1 and using the coupled state approximation for higher energies. Collisional rate constants for temperatures ranging from 5 to 200 K are deduced. A clear propensity rule in favour of Δj = -2 rotational transitions is observed. These rate coefficients are of great importance for the detection of HNS in interstellar medium. © 2016 The Authors.


Almenia S.,King Saud University | Mogren Al Mogren M.,King Saud University | Ben Abdallah D.,Riyadh Corporation of Technology | Linguerri R.,University Paris Est Creteil | Hochlaf M.,University Paris Est Creteil
Chemical Physics Letters | Year: 2016

We investigate VO2+ and VO3+ ions theoretically. The electronic computations are performed using multi reference configuration interaction approaches in conjunction with the aug-cc-pV5Z basis set. VO2+ potential possesses a Morse-like shape instead of the common volcanic shape since both the charge retaining (V2+ + O) and charge separating (V+ + O+) dissociation channels are almost coinciding in energy. Its intense blue color is due to the A2Π-X2Δ transition. We predict VO3+ as metastable. For bound states, we derived a set of accurate spectroscopic parameters. We estimate the adiabatic double and triple ionization energies of VO to be 22.5 eV and 50.9 eV. © 2016 Elsevier B.V. All rights reserved.


Mogren Al Mogren M.,King Saud University | Ben Abdallah D.,University of Tunis | Ben Abdallah D.,Riyadh Corporation of Technology | Hochlaf M.,University Paris Est Creteil
Chemical Physics | Year: 2015

Using multi reference configuration interaction methodology in connection with a large basis set, we show that GeO2+ is a metastable species either in the ground or in the electronically excited states. This confirms the observation of this dication in gas phase by mass spectrometry. In addition, we derived a set of accurate spectroscopic terms for GeO2+ bound states. At the MRCI/aug-cc-pV5Z level of theory, the adiabatic double ionization energy of GeO is computed to be ∼28.93 eV. © 2014 Elsevier B.V. All rights reserved.


Al Mogren M.M.,King Saud University | Denis-Alpizar O.,CNRS Institute of Molecular Sciences | Denis-Alpizar O.,University of Matanzas | Ben Abdallah D.,University of Tunis | And 5 more authors.
Journal of Chemical Physics | Year: 2014

Through the study of the C3(X̃1Σ g +) + He(1S) astrophysical relevant system using standard (CCSD(T)) and explicitly correlated (CCSD(T)-F12) coupled cluster approaches, we show that the CCSD(T)-F12/aug-cc-pVTZ level represents a good compromise between accuracy and low computational cost for the generation of multi-dimensional potential energy surfaces (PESs) over both intra- and inter-monomer degrees of freedom. Indeed, the CCSD(T)-F12/aug-cc-pVTZ 2D-PES for linear C3 and the CCSD(T)-F12/aug-cc-pVTZ 4D-PES for bent C 3 configurations gently approach those mapped at the CCSD(T)/aug-cc-pVXZ (X = T,Q) + bond functions level, whereas a strong reduction of computational effort is observed. After exact dynamical computations, the pattern of the rovibrational levels of the intermediate C3-He complex and the rotational and rovibrational (de-) excitation of C3 by He derived using both sets of PESs agree quite well. Since C3 shows a floppy character, the interaction PES is defined in four dimensions to obtain realistic collisional parameters. The C-C-C bending mode, which fundamental lies at 63 cm-1 and can be excited at very low temperatures is explicitly considered as independent coordinate. Our work suggests hence that CCSD(T)- F12/aug-cc-pVTZ methodology is the key method for the generation of accurate polyatomic - He/H2 multi-dimensional PESs. © 2014 AIP Publishing LLC.


Tebai Y.,Tunis el Manar University | Jaidane N.-E.,Tunis el Manar University | Ben Abdallah D.,Tunis el Manar University | Ben Abdallah D.,Riyadh Corporation of Technology | And 3 more authors.
Journal of Chemical Physics | Year: 2014

Using the recently developed explicitly correlated coupled cluster method in connection with the aug-cc-pVTZ basis set, we generated the three-dimensional potential energy surface (3D-PES) of the ground state of the Ar-BeO complex. This PES covers the regions of the global and local minima, the saddle point, and the dissociation of the complex. The PES is also used for the calculation of the rovibrational spectrum up to the dissociation limit. The high density of levels which is observed favors the mixing of the states and hence the occurrence of anharmonic resonances. The wavefunctions of the high rovibrational levels exhibit large amplitude motions in addition to strong anharmonic resonances. Our theoretical spectrum should be helpful in identifying the van der Waals modes of this complex in laboratory. © 2014 AIP Publishing LLC.


Mogren Al Mogren M.,King Saud University | Ajili Y.,Tunis el Manar University | Almania S.,King Saud University | Ben Abdallah D.,Tunis el Manar University | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

Using a well-established ab initio methodology to generate the potential energy surface of the MgO-He interacting system and a quantum close-coupling treatment of nuclear motion, we give the rotational (de-)excitation cross-sections and the collision rate coefficients for the first 16 rotational levels of the MgO molecule and He for temperatures ranging from 10 up to 300 K. A clear propensity rule in favour of Δj = 1 rotational transitions is observed. These data are compared with previous works on astrophysical oxygen-bearing diatomic species. This work should be useful for the eventual detection of the key metal-oxide MgO molecule in the circumstellar and interstellar media with current and future high-resolution telescopes. © 2015 The Authors.


Najar F.,Tunis el Manar University | Ben Abdallah D.,Tunis el Manar University | Ben Abdallah D.,Riyadh Corporation of Technology | Jaidane N.,Tunis el Manar University
Chemical Physics Letters | Year: 2014

Adiabatic and diabatic potential energy surfaces (PESs) of the ground and the first excited electronic states for the interaction of C2(X 1Σg +,a3Πu) +H(2S) system have been computed from the ab initio multi-reference configuration interaction wave functions including Davidson correction (MRCI + Q), using the augmented correlation-consistent valence quadruple-zeta (aug-cc-pVQZ) basis set of Dunning. Mixing angle and coupling potential have been calculated for all selected ab initio geometries. The C2 bond length was fixed at the experimental equilibrium distance re=2.348 bohr of C2(XX1Σg +) state. Quantum mechanical coupled states rotational dynamics application has been done on the ground adiabatic and diabatic PESs. © 2014 Elsevier B.V. All rights reserved.

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