DSpace at VNU: Theoretical investigations of BBS (singlet)- BSB (triplet) transformation on a potential energy surface obtained from neural network fitting

Accepted ManuscriptTheoretical Investigations of BBSsinglet→BSBtriplet Transformation on a Potential Energy Surface Obtained from Neural Network Fitting Hieu T.. Le, Theoretical Investig

Accepted Manuscript

Theoretical Investigations of BBS(singlet)→BSB(triplet) Transformation on a

Potential Energy Surface Obtained from Neural Network Fitting

Hieu T Nguyen-Truong, Cao Minh Thi, Hung M Le

DOI: http://dx.doi.org/10.1016/j.chemphys.2013.09.007

Please cite this article as: H.T Nguyen-Truong, C.M Thi, H.M Le, Theoretical Investigations ofBBS(singlet)→BSB(triplet) Transformation on a Potential Energy Surface Obtained from Neural Network Fitting,

Chemical Physics (2013), doi: http://dx.doi.org/10.1016/j.chemphys.2013.09.007

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Theoretical Investigations of BBS(singlet)→BSB(triplet) Transformation on a Potential Energy Surface Obtained from Neural

Network Fitting

Hieu T Nguyen-Truonga,c, Cao Minh Thib, Hung M Lea,∗

a

Faculty of Materials Science, University of Science, Vietnam National University, Ho

Chi Minh City, Vietnam

b

Nano-Materials Laboratory, Ho Chi Minh City University of Technology, Ho Chi Minh

City, Vietnam

c

Faculty of Electronics and Computer Science, Volgograd State Technical University, 28

Lenin Avenue, Volgograd 400131, Russia

Abstract

B2S, the simplest BnSm cluster, has been shown to exhibit an interestingground-state structure B3LYP/6-311G(d,p) calculations suggest that itsmost stable configuration is singlet linear B-B-S When promoted to the ex-cited triplet state, B2S adopts the B-S-B configuration (C2v point group) Tocharacterize its structural transformation, the lowest energy at each configu-ration is selected, and the neural network surface is developed with symmetryexchange incorporated The triplet potential energy is found to be 0.48 eVabove the ground state Subsequently, the nudged-elastic-band method isemployed to locate the BBS→BSB transition state It is found that the bar-rier height is 1.35 eV above the equilibrium singlet BBS energy (0.88 eV forthe reverse reaction) In addition, quasiclassical molecular dynamics withdifferent vibrational excitations shows that the reaction is accelerated whenthe bending vibrational mode of BBS is excited, while the activation of BBSstretching modes causes a negative effect

Keywords: B2S, electronic structure calculations, feed-forward neuralnetwork, symmetry exchange, potential energy surface, molecular dynamics

∗ Corresponding author Tel.: 84-838-350-831.

Email address: hung.m.le@hotmail.com (Hung M Le)

our definition, when B2S adopts the B-B-S linear structure, θ is 0◦

; in the159

172

where wi,j and bj are the weight and bias values of the first layer, respectively;193

f is a hyperbolic tangent function which is utilized to provide curvatures to194

the NN function The signals a1

j are later used as an input value for the195

geometric configuration is relatively close to the transition state predicted324

by our previous NEB optimization

a bending mode is low in energy (only 25 cm−1

, its activation with a small357

amount of energy is very effective in BBS→BSB conversion

Figure 1:

Figure 2:

Figure 3:

Figure 4:

TABLES

436

Table 1: Equilibrium structure (in ˚ A or deg) and vibrational wavenumber (cm −1 ) of

singlet BBS and triplet BSB given by B3LYP/6-311g(d,p) and CCSD(T)/aug-cc-pVTZ

calculations.

Singlet BBSGeometry BBS pi Symmetric Asymmetric

R1 R2 θ linear bend stretching stretching

CCSD(T)/aug-cc-pVTZ 1.620 3.386 0.00 179 567 1330

Triplet BSBGeometry Asymmetric B-S-B Symmetric

R1 R2 θ B-S stretching bending B-S stretching

CCSD(T)/aug-cc-pVTZ 1.814 1.814 53.20 660 735 1045

Triplet 0.48 1.33CCSD(T)/aug-cc-pVTZ Singlet 0.00 0.99

Triplet 0.64 1.55

Table 3: Minimum and maximum values of x 1 , x 2 , x 3 , cos θ, and E.

x1 x2 x3 cos θ E (eV)Minimum 3.1685 0.7724 1.6596 -1.0000 0.0000

Maximum 5.6213 1.2627 1.8565 1.0000 1.9999

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