Dynamics of the Hole-Capture Processes in Biphenyl and Poly(4-vinylbiphenyl):  A Direct ab Initio Trajectory Study

Abstract

Direct ab initio trajectory calculations have been applied to the ionization (i.e., hole-capture) processes of biphenyl (Bp) in order to shed light on hole-capture processes of Bp and poly(4-vinylbiphenyl) (PVB). The static ab initio calculations at several levels of theory showed that the neutral Bp has a nonplanar structure with a twist angle between benzene rings in the range φ ) 38-50°. The potential energy curve for the twist rotation of benzene rings was shallow for Bp. This twist angle was changed to 18-21°in biphenyl cation (Bp + ), which has a more planar structure and a more tight potential shape than those of Bp. Full dimensional direct ab initio trajectory calculations showed that the structure of Bp is spontaneously changed after the ionization: the nonplanar structure was changed to planar one after 120 fs, and then the twist angle vibrated between -40°and +40°with a time period of about 500 fs. The C-C bond distance in the connection site between two benzene rings was immediately shortened after the hole capture of Bp, and it vibrated in the range 1.375-1.481 Å. Direct PM3 dynamics calculations for the model compound composed of two-monomer units of PVB indicated that a hole is localized on one of the biphenyl groups at time zero, and then it is delocalized over the two side-groups after the structural relaxation. The mechanism of hole capture in Bp and in PVB was discussed on the basis of theoretical results.

Electronic structures of one-dimensional poly-fused selenophene radical cations: density functional theory study

“…To check the level of theory used in the calculations of the excitation energies, SAC-CI calculations were carried out for n = 1-4. Note that these levels of theory give reasonable features for several molecular device systems [13][14][15][16][17][19][20][21][22].…”

“…In particular, the origin of the hole conductivity was elucidated on the basis of theoretical results. In the present study, we extended previous techniques [13][14][15][16][17] to the molecular device Se(n).…”

“…In previous works [13][14][15][16][17], we investigated theoretically organic semiconductors and molecular devices by DFT, ab initio molecular orbital (MO), and direct ab initio dynamics methods. We elucidated the mechanism of hole conductivities in various molecular devices, such as poly(vinyl-biphenyl) [13], polysilane [14,15], and oligothiophene molecular devices [16,17].…”

“…We elucidated the mechanism of hole conductivities in various molecular devices, such as poly(vinyl-biphenyl) [13], polysilane [14,15], and oligothiophene molecular devices [16,17]. In particular, the origin of the hole conductivity was elucidated on the basis of theoretical results.…”

DFT and direct ab initio MD calculations of the gas hydrate: Hydrogen molecule trapped in water cluster (H2O)12

“…Therefore, we chose the basis sets carefully in the calculations. The geometry optimizations of the isolated molecule H 2 and the lattice water cluster were carried out at 11 levels of theory: the HF/LANL2MB, HF/ [6-311G(d,p) In order to obtain the temperature effect on the structure of the H 2 (H 2 O) 12 cluster at finite temperature, full-dimensional direct ab initio molecular dynamics (MD) calculations [11][12][13][14] were performed at the HF/[6-311G(d,p),3-21G*] level. The temperature was 50 K as a simulation temperature, which is defined by:…”