An accurate description of metal nanoparticle (NP)–support interactions is required for designing and optimizing NP catalytic systems because NP–support interactions may significantly impact NP stability and properties, such as catalytic activity. The ability to calculate NP interactions with amorphous supports, which are commonly used in industrial practice, is hampered because of a general lack of accurate atomically detailed model structures of amorphous surfaces. We have systematically studied relaxation processes of Pt13 NPs on amorphous silica using recently developed realistic model amorphous silica surfaces. We have modeled the NP relaxation process in multiple steps: hard-sphere interactions were first used to generate initial placement of NPs on amorphous surfaces, then Pt–silica bonds were allowed to form, and finally both the NP and substrate were relaxed with density functional theory calculations. We find that the amorphous silica surface significantly impacts the morphology and electronic structure of the Pt clusters. Both NP energetics and charge transfer from NP to the support depend linearly on the number of Pt–silica bonds. Moreover, we find that the number of Pt–silica bonds is determined by the silica silanol number, which is a function of the silica pretreatment temperature. We predict that catalyst stability and electronic charge can be tuned via the pretreatment temperature of the support materials. The extent of support effects suggests that experiments aiming to measure the intrinsic catalytic properties of very small NPs on amorphous supports will fail because the measurable catalytic properties will depend critically on metal–support interactions. The magnitude of support effects highlights the need for explicitly including amorphous supports in atomistic studies.

Organic piezoelectric materials are promising targets in applications such as energy harvesting or mechanical sensors and actuators. In a recent paper (Werling, K. A.; et al. J. Phys. Chem. Lett. 2013, 4, 1365–1370), we have shown that hydrogen bonding gives rise to a significant piezoelectric response. In this article, we aim to find organic hydrogen bonded systems with increased piezo-response by investigating different hydrogen bonding motifs and by tailoring the hydrogen bond strength via functionalization. The largest piezo-coefficient of 23 pm/V is found for the nitrobenzene–aniline dimer. We develop a simple, yet surprisingly accurate rationale to predict piezo-coefficients based on the zero-field compliance matrix and dipole derivatives. This rationale increases the speed of first-principles piezo-coefficient calculations by an order of magnitude. At the same time, it suggests how to understand and further increase the piezo-response. Our rationale also explains the remarkably large piezo-response of 150 pm/V and more for another class of systems, the “molecular springs” (Marvin, C.; et al. J. Phys. Chem. C 2013, 117, 16783–16790.).

The piezoelectric properties of 2-methyl-4-nitroaniline crystals were explored qualitatively and quantitatively using an electrostatically embedded many-body (EE-MB) expansion scheme for the correlation energies of a system of monomers within the crystal. The results demonstrate that hydrogen bonding is an inherently piezoelectric interaction, deforming in response to the electrostatic environment. We obtain piezo-coefficients in excellent agreement with the experimental values. This approach reduces computational cost and reproduces the total resolution of the identity (RI)-Møller–Plesset second-order perturbation theory (RI-MP2) energy for the system to within 1.3 × 10–5%. Furthermore, the results suggest novel ways to self-assemble piezoelectric solids and suggest that accurate treatment of hydrogen bonds requires precise electrostatic evaluation. Considering the ubiquity of hydrogen bonds across chemistry, materials, and biology, a new electromechanical view of these interactions is required.Keywords: electromechanical distortion; many-body expansion; self-assembly;