Dithienylethene-Based Single Molecular Photothermal Linear Actuator

By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, open form (compressed, UV OFF) and closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level.     

Comparison between 6-31 + bond functions and 6-31 G* basis sets in UMP calculations of dissociation energies of the first row element compounds. I

A basis set with bond functions (6-31G + BF) has been tested for its applicability to calculation of dissociation energies of single and multiple bonds by Moeller-Plesset perturbation theory at the second and third orders. Results have been compared with those calculated in the 6-31G* basis set. The 6-31G + BF basis at the MP 2 and MP 3 levels yields better results than 6-31G* basis and the time consumption is less as well. Consideration of the bond functions on the bonds neighboring the bond being broken has no significant influence on the dissociation energies either at the SCF or at the MP 2 levels. If both reactants and products can be characterized by two-center bonds, the 6-31G + BF basis and UMP2 variant of perturbation theory can be recommended for practical calculation of D_e values, especially for the systems where the use of more exact bases is rather difficult.     

Calculation of rotational barriers in amorphous polymers

The Monte Carlo method was used for generation of amorphous polyethylene configurations on a diamond lattice. Chain building was performed on the tetrahedral lattice of edges 36, 62 and 43 Å with periodic boundary conditions imposed.32 chains were generated, each with a length of 100 CH₂-groups (resulting density = 0.81 g·cm⁻³). Small spherical volumes with a radius of 10 Å were chosen at random from the total volume for the calculation of rotational barriers. The rotating bond was chosen to be close to the center of this sphere. We employed the method of molecular mechanics in order to calculate the rotational barriers. The calculation was made for 578 rotating bonds and the obtained distribution of rotational barriers is approximated by the corresponding Γ-distribution.     

Extended Hamiltonian Hessenberg Matrices arise in Projection based Model Order Reduction

We show that extended Hamiltonian Hessenberg matrices arise naturally in projection-based model order reduction. Therefore we reduce a large dynamical system by projecting it on an extended Krylov subspace. The eigenvalues of the reduced order model can then be computed directly by applying the extended Hamiltonian QR algorithm. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)