Recent measurements show that organic materials with a conjugated benzothieno-benzothiophene (BTBT) core exhibit unprecedented charge-carrier mobilities, dramatically influenced by the size of the side-chains. Using a multitude of computational tools, we, in depth, calculate the molecular ordering and charge-transport of these materials to rationalize the side-chain dependence. The reported experimental hole mobilities typically fall within the range of 1-100 cm2 V-1 s-1, therefore we employ both band transport models using deformation-potential theory based on DFT-D3 methodology and hopping transport using kinetic Monte Carlo simulations employing Marcus-Levich-Jortner charge-transfer theory. Band transport calculations are performed in a perfect lattice, considered as a structurally ordered morphology, while hopping transport calculations are performed for both ordered and disordered morphologies based on molecular dynamics simulations. We find that intrinsic mobility in BTBTs is critically controlled by the alkyl chain length; typically, longer alkyl side-chains regulate intrinsic disorder, cause improved balance between different transport directions and, ultimately, lead to enhanced charge-carrier mobility.

A novel implementation of the self-consistent field (SCF) procedure specifically designed for high-performance execution on multiple graphics processing units (GPUs) is presented. The algorithm offloads to GPUs the three major computational stages of the SCF, namely, the calculation of oneelectron integrals, the calculation and digestion of electron repulsion integrals, and the diagonalization of the Fock matrix, including SCF acceleration via DIIS. Performance results for a variety of test molecules and basis sets show remarkable speedups with respect to the state-of-the-art parallel GAMESS CPU code and relative to other widely used GPU codes for both single and multi-GPU execution. The new code outperforms all existing multi-GPU implementations when using eight V100 GPUs, with speedups relative to Terachem ranging from 1.2× to 3.3× and speedups of up to 28× over QUICK on one GPU and 15× using eight GPUs. Strong scaling calculations show nearly ideal scalability up to 8 GPUs while retaining high parallel efficiency for up to 18 GPUs.

Designed site-directed dimerization of the monoanion radicals of a π-bowl in the solid state is reported. Dibenzo[a,g]corannulene (C H ) was selected based on the asymmetry of the charge/spin localization in the C H anion. Controlled one-electron reduction of C H with Cs metal in diglyme resulted in crystallization of a new dimer, [{Cs (diglyme)} (C H -C H ) ] (1), as revealed by single crystal X-ray diffraction study performed in a broad range of temperatures. The C-C bond length between two C H bowls (1.560(8) Å) measured at -143 °C does not significantly change upon heating of the crystal to +67 °C. The single σ-bond character of the C-C linker is confirmed by calculations. The trans-disposition of two bowls in 1 is observed with the torsion angles around the central C-C bond of 172.3(5)° and 173.5(5)°. A systematic theoretical evaluation of dimerization pathways of C H radicals confirmed that the trans-isomer found in 1 is energetically favored.

Many-body dispersion has gained considerable attention over the past decade, particularly for condensed phase systems. However, quantitatively accurate studies of many-body dispersion have only recently become feasible due to challenges in reliability and accuracy. Currently available methodologies for calculating many-body dispersion have been challenged, with recent evidence suggesting, for example, that dispersioncorrected density functional theory (DFT) schemes cannot consistently predict many-body dispersion accurately. This study evaluates many-body dispersion energies using a composite approach that employs singles and doubles coupled cluster theory with perturbative/noniterative triples, CCSD(T), combined with an extrapolation to the complete basis set (CBS) limit. The combined CCSD(T)/CBS approach is applied to Ar n and (H 2 O) n , n = 3−10, clusters, and a new data set called S22(3), which includes trimers generated based on the S22 data set. In these systems, the many-body dispersion provides a very small contribution to the total interaction energy of all of the systems studied, generally 3% or less of the total interaction energy. Two-body dispersion is the dominant dispersion contribution and many-body dispersion contributes no more than 5.7% of the total dispersion energy, generally staying below 2%.