We have employed conventional ab initio and density-functional-theory (DFT) methods to study the structure, stability and electric polarizability of small gallium arsenide clusters ${\mathrm{Ga}}_n{\mathrm{As}}_n$. We relied on purpose-oriented, carefully optimized basis sets of Gaussian-type functions. We have calculated both the mean dipole polarizability $\left(\overline{\alpha }\right)$ and the anisotropy $\left(\mathrm{\Delta }\alpha \right)$. Our results show that the differential-per-atom polarizability of the most stable isomers decreases rapidly with cluster size. Compared to the ab initio results, the widely used Becke’s three-parameter exchange DFT functional with the Lee, Yang, and Parr correlation functional and Becke’s three-parameter exchange DFT functional with Perdew and Wang’s 1991 gradient-corrected correlation functional density-functional-theory methods follow clearly the trend of the differential-per-atom polarizability ${\overline{\alpha }}_{\mathrm{diff}}∕\mathrm{atom}$ for the most stable isomers and predict values closer to the self-consistent field method but distinctly lower than second-order Møller-Plesset perturbation theory. All methods predict a positive value for the dimer, ${\overline{\alpha }}_{\mathrm{diff}}∕\mathrm{atom}$ $\left({\mathrm{Ga}}_2{\mathrm{As}}_2\right)>0$.

Styrene–butyl acrylate (S–BuA) copolymers were synthesized by nitroxide-mediated controlled radical polymerization using an alkoxyamine as an initiator. Using different synthetic methodologies, statistical copolymers were be obtained by batch nitroxide mediated polymerization while the gradient composition was a forced gradient by continuous addition of S during BuA polymerization (semi-batch process). These gradient copolymers have been studied by ¹H NMR and size exclusion chromatography to characterize the gradient composition molecular structure. The evolution of the composition was correlated with the glass transition temperature (T_g) of the copolymers. The gradient copolymers exhibit one T_g with a value in between the T_g of polystyrene and poly(butyl acrylate), indicating that the materials did not present well defined microphase separation. Specific organization at the air–polymer interface of such copolymers has also been demonstrated by comparison between classical and attenuated total reflection (ATR) Fourier transform infra-red spectra. This bulk soft matter assembly was confirmed by AFM analysis, which showed a different morphology at the surface and in the bulk following removal of the top layer. Moreover, for the most well defined gradient composition, a specific nano-structuring was demonstrated by small angle neutron scattering. The preliminary rheological properties of these gradient copolymers were studied and are discussed in relation with their molecular structure.

Borazino-doped nanographenes belong to a special class of flat heteroaromatic networks comprising one or more fully formed borazino (B₃N₃) units in their framework. These systems carry the same number of electrons and feature similar structural forms as pristine nanographenes; however, they are characterized by different optoelectronic properties. As their full carbon analogues, borazino-doped graphene molecules could serve as excellent candidate molecules for flexible organic electronic and optical devices. In this study, we provided the results of a systematic study dealing with the effect of borazino units on the quadratic microscopic nonlinear optical (NLO) properties of finite graphene sections. These symmetry-dependent quantities describe the nonlinear polarization (hyperpolarization) of the electron cloud of molecules in the presence of external electric fields and they are associated with fundamental processes of extreme technological interest in the realm of nonlinear optics. More precisely, we investigated the evolution of the first dipole hyperpolarizability in several, purposely chosen, borazino-doped graphene flakes and ribbons, relying on long-range corrected density functional methods. Our results indicate that the presence of inorganic benzene in the honeycomb structure of graphene finite sections gives rise to some impressive structure–property variations driven by local electron delocalization effects. The take home message of this study suggests that borazino doping can deliver a vast assortment of nanographene molecules bearing amplified octupolar and/or dipolar NLO responses that can be fine-tuned by applying minor modifications in the structure and morphology of their edges.

An automatic Born-Oppenheimer potential energy surface (PES) generation method AGAPES is presented designed for the calculation of vibrational spectra of large rigid and semi-rigid polyatomic molecules within the mid-infrared energy range. An adaptive approach guided by information from intermediate vibrational calculations in connection with a multi-mode expansion of the PES in internal valence coordinates is used and its versatility is tested for a selection of molecules: HNO, HClCO, and formaldoxime. Significant computational savings are reported. The possibility of linear scaling of the sampling grid size with the molecular size due to decrease of correlation of remote coordinates in large molecules is examined and finally, possible improvements are suggested.

Using an effective generation algorithm coupled with a PBE0/LANL2DZdp level of theory, 905 stable structures of Sin (n=3,15) have been found. This global search algorithm of minima exploration includes two original parts: the spheroidal generation, allowing the generation of rings, sphericals, m rings cylinders, and planar structures, and the raking optimization, which discards step by step the conformations that become physically unreasonable during the optimization process. The 142 isomers lying below 1 eV are reported and include the 28 structures reported in the literature. Conformational energies are well reproduced with respect to the values previously published (ΔE=0,00±0,09 eV).