XVIth International Workshop on
Quantum Systems in
Chemistry and Physics
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Ab initio calculations of methane dimer interaction energies and
molecular dynamics simulation of fluid methane
Arvin Huang-Te Li and Sheng D. Chao
Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan ROC.

Intermolecular interaction potentials of the methane dimers have been calculated for 12 symmetric conformations using the second-order Møller-Plesset (MP2) perturbation theory and the coupled-cluster with single and double and perturbative triple excitations (CCSD(T)) theory. With increasing basis size, a large basis set (aug-cc-pVTZ) is required to converge the binding energy at a chemical accuracy (~0.01 kcal/mol). Only the BSSE corrected results systematically converge to the destined potential curve with increasing basis size. The binding energy calculated and the equilibrium bond length using the CCSD(T) method are close to the results at the basis set limit. For molecular dynamics (MD) simulation, a 4-site potential model with sites located at the hydrogen atoms was used to fit the ab initio potential data. MD simulations using the ab initio PES show good agreement on both the atom-wise radial distribution functions and the self-diffusion coefficients over a wide range of experimental conditions.
Ultrafast electronic motion in hydrogen molecular ion induced by a high power intense laser
H. Mineo1 , Y. Teranishi2 , S.D. Chao1, and S.H. Lin3,4
1 Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan ROC
2 Department of Physics, National Chiao Tung University, Hsinchu 300, Taiwan
3 Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan ROC
4 Institute of Applied Chemistry, Institute of Molecular Science, Chiao-Tung University, Hsin-Chu, Taiwan ROC
In this report we show how to control the electronic localization in a molecular ion on attosecond time scale by high intense laser based on two different excitation mechanisms, i.e., one takes place during ionization, and the other one sequentially takes place after the ionization [1]. The electronic excited states of hydrogen molecular ion are created during the ionization by taking the configuration interaction (CI) mixing of neutral molecule into account. Photoionization process is calculated by the generalized Keldysh-Faisal-Reiss (KFR) theory [2]. We detect ultrafast oscillatory electronic motion between two atoms in a hydrogen molecular ion due to the creation of excited states during the ionization.

[1] H. Mineo, Y. Teranishi, S.D. Chao, and S.H. Lin, CPL 499, 45 (2010).
[2] L. V. Keldysh, Sov. Phys. JETP 20, 1307 (1965); F. H. M. Faisal, J. Phys. B6, L89 (1973); H. R. Reiss, Phys. Rev. A22, 1786 (1980).


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