Using the non-equilibrium Green functions （NEGF） and density functional theory （DFT） method, a calculation of the transport properties of the Au-di-thiol-benzene （DTB） sandwich system was performed. The results show that both the remaining H atom at the end of the DTB molecule and the increased S-Au surface distance will decrease the electronic transport significantly. The applied bias would change the symmetry of the system electronic structure. Our result was qualitatively consistent with the experiment, but there existed a gap of three orders of magnitude, and this was attributed to the different coupling geometry between the theoretical work and the experiment.
The density functional theory (DFT) combining with the non-equilibrium Green functions (NEGF) method is applied to the study of the electronic transport properties for a Di-thiol-benzene (DTB) molecule coupled to two Au(111) surfaces. The dependence of the transport properties on the bias, the coupling geometry of the molecule-electrode interface, and the intermolecular interaction are examined in detail. The results show that the existence of the hydrogen atom at the end of the DTB molecule would significantly decrease the transmission coefficients, and then the differential conductance (dI/dV). By changing the position of the DTB molecule located between two electrodes a maximum value of calculated current is observed. It is also found that the intermolecular interaction will strongly influence the transport properties of the system studied.
QI Yuanhua1,2, GUAN Daren1 & LIU Chengbu1 1. Institute of Theoretical Chemistry, Shandong University, Jinan 250100, China
The highly excited vibrational states of asymmetric linear tetratomic molecules are studied in the framework of Lie algebra. By using symmetric group U1(4) U2(4) U3(4), we construct the Hamiltonian that includes not only Casimir operators but also Majorana operators M12,M13 and M23, which are useful for getting potential energy surface and force constants in Lie algebra method. By Lie algebra treatment, we obtain the eigenvalues of the Hamiltonian, and make the concrete calculation for molecule C2HF.
The Hamiltonian describing rotational spectra of linear triatomic molecules has been derived by using the dynamical Lie algebra of symmetry group U1(4)?U24. After rovibrational interactions being considered, the eigenvalue expression of the Hamiltonian has the form of term value equation commonly used in spectrum analysis. The molecular rotational constants can be obtained by using the expression and fitting it to the observed lines. As an example, the rotational levels ofv 2 band for transition (0200–0110) of molecules N2O and HCN have been fitted and the fitting root-mean-square errors (RMS) are 0.00001 and 0.0014 cm?1, respectively.
