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A new potential energy surface for the H2S system and dynamics study on the S((1)D) + H2(X(1)Σg(+)) reaction.

Yuan J, He D, Chen M - Sci Rep (2015)

Bottom Line: The ab initio energies are obtained from multireference configuration interaction calculations with a Davidson correction using basis sets of quadruple zeta quality.Both forward and backward scatterings can be observed as expected for a barrierless reaction with a deep well on the PES.The calculated integral cross sections and differential cross sections are in good agreement with the experimental results.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Materials Modification by Laser, Electron, and Ion Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, PR China.

ABSTRACT
We constructed a new global potential energy surface (PES) for the electronic ground state ((1)A') of H2S based on 21,300 accurate ab initio energy points over a large configuration space. The ab initio energies are obtained from multireference configuration interaction calculations with a Davidson correction using basis sets of quadruple zeta quality. The neural network method is applied to fit the PES, and the root mean square error of fitting is small (1.68 meV). Time-dependent wave packet studies for the S((1)D) + H2(X(1)Σg(+)) → H((2)S) + SH(X(2)Π) reaction on the new PES are conducted to study the reaction dynamics. The calculated integral cross sections decrease with increasing collision energy and remain fairly constant within the high collision energy range. Both forward and backward scatterings can be observed as expected for a barrierless reaction with a deep well on the PES. The calculated integral cross sections and differential cross sections are in good agreement with the experimental results.

No MeSH data available.


Related in: MedlinePlus

Minimum energy paths for H2S (1A′) PES at four S-H-H angles.
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f2: Minimum energy paths for H2S (1A′) PES at four S-H-H angles.

Mentions: Table 1 shows the equilibrium structural parameters of the new H2S PES. The experimental results30 and the previous theoretical results from two analytical PESs1213 are also listed in the table. For both the geometry and the energy, the agreement between the calculated and experimental results is good, and our results are closer to the experimental data. The contour maps for the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction in internal coordinates at four S-H-H angles (45°, 90°, 135°, and 180°) are shown in Figure 1. In each map, there are two valleys: the left valley corresponds H(2S) + SH(X2Π), and the valley at the bottom corresponds to S(1D) + H2(X1Σg+). There are wells at three angles (45°, 90° and 135°), and the wells are deeper for larger angles. For the angle of 180°, there is no well but there is a barrier, indicating that the title reaction with a sufficiently low collision energy cannot occur through the S-H-H collinear path. For a better understanding of the characteristics of the PES, the minimum energy paths (MEPs) of the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction at the four S-H-H angles are shown in Fig. 2. The exothermicity for the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction is 0.15 eV. For the S-H-H angles (45°, 90° and 135°), the depths of the wells are 0.36 eV, 1.90 eV and 4.29 eV, respectively. For the S-H-H angle of 180°, the barrier height is 0.34 eV. Figure 3(a) shows an energy plot for a sulfur atom moving around a H2 molecule with a fixed bond length at the equilibrium distance. The zero energy is set as the energy in the configuration when the sulfur atom is far from the H2 molecule. There is a well 1.58 eV deep at x = 0.0 angstrom, y = 1.37 angstrom. For the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction, as the sulfur atom moves slowly to the H2 molecular, it is attracted to the well. Therefore, it is expected that the insertion reaction plays an important role in the title reaction. Figure 3(b) shows an energy plot for a hydrogen atom moving around a SH molecule of which the bond length is fixed at the equilibrium distance and the zero energy is set as the energy in the configuration when the hydrogen atom is far from the SH molecule. There is a deep well (4.15 eV) close to the sulfur atom at of x = 0.74 angstrom, y = 1.33 angstrom.


A new potential energy surface for the H2S system and dynamics study on the S((1)D) + H2(X(1)Σg(+)) reaction.

Yuan J, He D, Chen M - Sci Rep (2015)

Minimum energy paths for H2S (1A′) PES at four S-H-H angles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4592959&req=5

f2: Minimum energy paths for H2S (1A′) PES at four S-H-H angles.
Mentions: Table 1 shows the equilibrium structural parameters of the new H2S PES. The experimental results30 and the previous theoretical results from two analytical PESs1213 are also listed in the table. For both the geometry and the energy, the agreement between the calculated and experimental results is good, and our results are closer to the experimental data. The contour maps for the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction in internal coordinates at four S-H-H angles (45°, 90°, 135°, and 180°) are shown in Figure 1. In each map, there are two valleys: the left valley corresponds H(2S) + SH(X2Π), and the valley at the bottom corresponds to S(1D) + H2(X1Σg+). There are wells at three angles (45°, 90° and 135°), and the wells are deeper for larger angles. For the angle of 180°, there is no well but there is a barrier, indicating that the title reaction with a sufficiently low collision energy cannot occur through the S-H-H collinear path. For a better understanding of the characteristics of the PES, the minimum energy paths (MEPs) of the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction at the four S-H-H angles are shown in Fig. 2. The exothermicity for the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction is 0.15 eV. For the S-H-H angles (45°, 90° and 135°), the depths of the wells are 0.36 eV, 1.90 eV and 4.29 eV, respectively. For the S-H-H angle of 180°, the barrier height is 0.34 eV. Figure 3(a) shows an energy plot for a sulfur atom moving around a H2 molecule with a fixed bond length at the equilibrium distance. The zero energy is set as the energy in the configuration when the sulfur atom is far from the H2 molecule. There is a well 1.58 eV deep at x = 0.0 angstrom, y = 1.37 angstrom. For the S(1D) + H2(X1Σg+) → H(2S) + SH(X2Π) reaction, as the sulfur atom moves slowly to the H2 molecular, it is attracted to the well. Therefore, it is expected that the insertion reaction plays an important role in the title reaction. Figure 3(b) shows an energy plot for a hydrogen atom moving around a SH molecule of which the bond length is fixed at the equilibrium distance and the zero energy is set as the energy in the configuration when the hydrogen atom is far from the SH molecule. There is a deep well (4.15 eV) close to the sulfur atom at of x = 0.74 angstrom, y = 1.33 angstrom.

Bottom Line: The ab initio energies are obtained from multireference configuration interaction calculations with a Davidson correction using basis sets of quadruple zeta quality.Both forward and backward scatterings can be observed as expected for a barrierless reaction with a deep well on the PES.The calculated integral cross sections and differential cross sections are in good agreement with the experimental results.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Materials Modification by Laser, Electron, and Ion Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, PR China.

ABSTRACT
We constructed a new global potential energy surface (PES) for the electronic ground state ((1)A') of H2S based on 21,300 accurate ab initio energy points over a large configuration space. The ab initio energies are obtained from multireference configuration interaction calculations with a Davidson correction using basis sets of quadruple zeta quality. The neural network method is applied to fit the PES, and the root mean square error of fitting is small (1.68 meV). Time-dependent wave packet studies for the S((1)D) + H2(X(1)Σg(+)) → H((2)S) + SH(X(2)Π) reaction on the new PES are conducted to study the reaction dynamics. The calculated integral cross sections decrease with increasing collision energy and remain fairly constant within the high collision energy range. Both forward and backward scatterings can be observed as expected for a barrierless reaction with a deep well on the PES. The calculated integral cross sections and differential cross sections are in good agreement with the experimental results.

No MeSH data available.


Related in: MedlinePlus