Abstract: Electron transport properties of the (GaAs)n(n=1-4) linear atomic chains, which are sandwiched between two infinite Au(100)-33 leads, are investigated with a combination of density functional theory and non-equilibrium Greens function method from first principle. We simulate the Au-(GaAs)n-Au nanoscale junctions breaking process, optimize the geometric structures of four kinds of junctions, calculate the cohesion energies and equilibrium conductances of junctions at different distances. The calculation results show that there is a stable structure for each nanoscale junction. The average bond-lengths of Ga-As in each chain at equilibrium positions for stable structure are 0.220 nm, 0.224 nm, 0.223 nm, 0.223 nm, respectively. The corresponding equilibrium conductances are 2.328G0, 1.167G0, 0.639G0, and 1.237G0, respectively. It means that each of all the junctions has a good conductivity. We calculate the transmission spectra of the all the chains. With the increase of atomic number in the (GaAs)n (n=1-4) chains, there appears no oscillation phenomenon for the equilibrium conductance. We calculate the projected densities of states of all nanoscale junctions at equilibrium positions, and the results show that electronic transport channel is mainly contributed by the px and py orbital electrons of Ga and As atoms. In the voltage range of 0-2 V, we calculate the current-voltage characteristics of junctions at equilibrium positions. With the increase of external bias, the current increases, and the I-V curves of junctions show linear characteristics for the (GaAs)n (n=1-3) atomic chains. However, there appears a negative differential resistance phenomenon in each of the voltage ranges of 0.6-0.7 V and 0.8-0.9 V for the (GaAs)4 linear atomic chain.

Abstract: The ground structure of Si60 clusters, which was obtained by optimization when using the density functional theory method, is a fullerene structure with C1 point group, a diameter 1.131 nm, the average bond length 0.239 nm, and the difference between the energies of the lowest unoccupied molecular orbital and the highest occupied molecular orbital is 0.72 eV. A Si60 cluster with optimized structure is sandwiched between two semi-infinite Au(100)-44 electrodes, and the Au-Si60-Au molecular junctions is constructed, whose electron transport properties is investigated with a combination of density functional theory and non-equilibrium Green's function method. When the distance between the two electrodes is 1.74 nm, the equilibrium conductance of the junctions is 1.93 G0 (G0=2e2/h). In the range of voltage from -2.02.0 V, we have calculated the current and conductance under different voltages, and find that the Ⅰ-Ⅴ curve of the junctions show linear characteristics. We also analyze the properties of transport from transmission and frontier molecular orbitals, and discuss the relationship of transfer charge with conductance.

Abstract: Electron transport properties of GaAs cluster, which is sandwiched between two semi-infinite Au(100)-3×3 electrodes in four different anchoring configurations (top-top, top-hollow, hollow-top, hollow-hollow), is investigated using the combination of density functional theory and non-equilibrium Green's function method. We optimize the geometry of junctions at different distances, simulate the breaking process of Au-GaAs-Au junctions, calculate the cohesion energy and conductance of the junctions as functions of distance dz, and obtain the most stable structure when the distances are set at 1.389 nm, 1.145 nm, 1.145 nm, 0.861 nm, respectively. For stable structures, the Ga-As bond lengths of the junctions is 0.222 nm, 0.235 nm, 0.227 nm, 0.235 nm, respectively. The equilibrium conductances are 2.33 G0, 1.20 G0, 1.90 G0, 1.69 G0,respectively. All junctions have large conductance. In the range of voltage from -1.2–1.2 V, the I-V curve of the junctions shows linear characteristics.

Abstract: 〈sec〉Potential energy curves (PECs), permanent dipole moments (PDMs) and transition dipole moments (TMDs) of five Λ-S states of SeH〈sup〉−〈/sup〉 anion are calculated by the MRCI + 〈i〉Q〈/i〉 method with ACVQZ-DK basis set. The core-valence corrections, Davidson corrections, scalar relativistic corrections, and spin-orbit coupling (SOC) effects are also considered. In the CASSCF step, Se(1s2s2p3s3p) shells are put into the frozen orbitals, which are not optimized. Six molecular orbitals are chosen as active space, including H(1s) and Se(4s4p5s) shells, and eight electrons are distributed in a (4, 1, 1, 0) active space, which is referred to as CAS (8, 6), and the Se(3d) shell is selected as a closed-shell, which keeps doubly occupation. In the MRCI step, the remaining Se(3d) shell is used for core-valence calculations of SeH〈sup〉−〈/sup〉 anion. The SOC effects are taken into account in the one- and two- electron Breit-Pauli operators.〈/sec〉〈sec〉The b〈sup〉3〈/sup〉Σ〈sup〉+〈/sup〉 state is a repulsive state. Other excited states are bound, and all states possess two potential wells. The 〈inline-formula〉〈tex-math id="M13"〉\begin{document}$ {{\rm{b}}^{{3}}}\Sigma _{{0^ - }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M13.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M13.png"/〉〈/alternatives〉〈/inline-formula〉 and 〈inline-formula〉〈tex-math id="M14"〉\begin{document}$ {{\rm{b}}^3}\Sigma _{{1}}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M14.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M14.png"/〉〈/alternatives〉〈/inline-formula〉 both turn into bound states when the SOC effect is considered. All spectroscopic parameters of Λ-S states and Ω states are reported for the first time. The TDMs of the 〈inline-formula〉〈tex-math id="M15"〉\begin{document}$ {{\rm{A}}^{{1}}}{\Pi _{{1}}} \leftrightarrow {{\rm{X}}^{{1}}}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M15.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M15.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M16"〉\begin{document}$ {{\rm{a}}^{{3}}}{\Pi _{{1}}} \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M16.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M16.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M17"〉\begin{document}$ {{\rm{a}}^{{3}}}{\Pi _{{{{0}}^{{ + }}}}} \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M17.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M17.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M18"〉\begin{document}$ {{\rm{A}}^{{1}}}{\Pi _{{1}}} \leftrightarrow {{\rm{a}}^{{3}}}{\Pi _{{1}}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M18.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M18.png"/〉〈/alternatives〉〈/inline-formula〉, and 〈inline-formula〉〈tex-math id="M19"〉\begin{document}$ {{\rm{A}}^{{1}}}{\Pi _{{1}}} \leftrightarrow {{\rm{a}}^{{3}}}{\Pi _{{{{0}}^{{ + }}}}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M19.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M19.png"/〉〈/alternatives〉〈/inline-formula〉 transitions are also calculated. The TDMs of the 〈inline-formula〉〈tex-math id="M20"〉\begin{document}$ {{\rm{A}}^{{1}}}{\Pi _{{1}}} \leftrightarrow {{\rm{X}}^{{1}}}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M20.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M20.png"/〉〈/alternatives〉〈/inline-formula〉 and 〈inline-formula〉〈tex-math id="M21"〉\begin{document}$ {{\rm{a}}^{{3}}}{\Pi _{{1}}} \leftrightarrow {{\rm{X}}^{{1}}}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M21.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M21.png"/〉〈/alternatives〉〈/inline-formula〉 transitions are large in the Franck-Condon region, which are about –2.05 Debye (D) and 1.45 D at 〈i〉R〈/i〉〈sub〉e〈/sub〉. Notably, the TDMs of the 〈inline-formula〉〈tex-math id="M22"〉\begin{document}$ {{\rm{a}}^3}{\Pi _{{{{0}}^{{ + }}}}} \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M22.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M22.png"/〉〈/alternatives〉〈/inline-formula〉 transition cannot be ignored. The value of TDM at 〈i〉R〈/i〉〈sub〉e〈/sub〉 equals –0.15 D.〈/sec〉〈sec〉Based on the accurately PECs and PDMs, the values of Franck-Condon factor 〈i〉f〈/i〉〈sub〉〈i〉υ〈/i〉′〈i〉υ〈/i〉″〈/sub〉, vibrational branching ratio 〈i〉R〈/i〉〈sub〉〈i〉υ〈/i〉′〈i〉υ〈/i〉″〈/sub〉 and radiative coefficient of the 〈inline-formula〉〈tex-math id="M23"〉\begin{document}$ {{\rm{a}}^{{3}}}{\Pi _{{1}}} \leftrightarrow {{\rm{X}}^{{1}}}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M23.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M23.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M24"〉\begin{document}$ {{\rm{a}}^{{3}}}{{{\Pi }}_{{{{0}}^{{ + }}}}} \leftrightarrow {{\rm{X}}^{{1}}}{{\Sigma }}_{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M24.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M24.png"/〉〈/alternatives〉〈/inline-formula〉, and 〈inline-formula〉〈tex-math id="M25"〉\begin{document}$ {{\rm{A}}^{{1}}}{\Pi _{{1}}} \leftrightarrow {{\rm{X}}^{{1}}}\Sigma _{{0^ + }}^ + $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M25.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M25.png"/〉〈/alternatives〉〈/inline-formula〉 transitions are also calculated. Highly diagonally distributed Franck-Condon factor 〈i〉f〈/i〉〈sub〉00〈/sub〉 and the values of vibrational branching ratio 〈i〉R〈/i〉〈sub〉00〈/sub〉 of the 〈inline-formula〉〈tex-math id="M26"〉\begin{document}$ {{\rm{a}}^{{3}}}{\Pi _{{1}}}(\upsilon ') \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + (\upsilon '')$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M26.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M26.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M27"〉\begin{document}$ {{\rm{a}}^{{3}}}{\Pi _{{0^ + }}}(\upsilon ') \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + (\upsilon '')$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M27.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M27.png"/〉〈/alternatives〉〈/inline-formula〉, and 〈inline-formula〉〈tex-math id="M28"〉\begin{document}$ {{\rm{A}}^1}{\Pi _1}(\upsilon ') \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + (\upsilon '')$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M28.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M28.png"/〉〈/alternatives〉〈/inline-formula〉 transitions are obtained, respectively. Spontaneous radiation lifetimes of the 〈inline-formula〉〈tex-math id="M29"〉\begin{document}$ {{\rm{a}}^3}{\Pi _{{1}}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M29.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M29.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M30"〉\begin{document}$ {{\rm{a}}^3}{\Pi _{{{{0}}^{{ + }}}}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M30.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M30.png"/〉〈/alternatives〉〈/inline-formula〉, and 〈inline-formula〉〈tex-math id="M31"〉\begin{document}$ {{\rm{A}}^1}{\Pi _{{1}}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M31.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M31.png"/〉〈/alternatives〉〈/inline-formula〉 excited states are all short for rapid laser cooling. The influences of intervening states of the 〈inline-formula〉〈tex-math id="M32"〉\begin{document}$ {{\rm{A}}^1}{\Pi _1}(\upsilon ') \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + (\upsilon '')$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M32.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M32.png"/〉〈/alternatives〉〈/inline-formula〉 transition can be ignored. The proposed cooling wavelengths using the 〈inline-formula〉〈tex-math id="M33"〉\begin{document}$ {{\rm{a}}^3}{\Pi _{{1}}}(\upsilon ') \leftrightarrow {{\rm{X}}^{{1}}}\Sigma _{{0^ + }}^ + (\upsilon '')$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M33.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M33.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M34"〉\begin{document}$ {{\rm{a}}^{{3}}}{\Pi _{{0^ + }}}(\upsilon ') \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + (\upsilon '')$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M34.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M34.png"/〉〈/alternatives〉〈/inline-formula〉, and 〈inline-formula〉〈tex-math id="M35"〉\begin{document}$ {{\rm{A}}^1}{\Pi _1}(\upsilon ') \leftrightarrow {{\rm{X}}^1}\Sigma _{{0^ + }}^ + (\upsilon '')$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M35.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201413_M35.png"/〉〈/alternatives〉〈/inline-formula〉 transitions are all in the visible region.〈/sec〉