Constructing Predictive Implicit Solvent Models: Insights from Exploring Potential Parameter Space and Property Predictions.

Implicit solvent (IS) models enhance the efficiency of simulating liquid systems, but those based on the potential of mean force calculations using explicit solvent (ES) models often fail to capture the solute structure and assembly dynamics under various conditions. This study examines the relationships between the parameter space of IS models and their predictive capabilities regarding solute structure and assembly dynamics, focusing on NaCl solutions and protein-bound silica colloidal nanoparticles. For NaCl solutions, models developed using concentration-dependent dielectric constants generally lack efficacy, and their effectiveness in predicting high-concentration liquid structures varies based on the ES model used.

Microscopic mechanism of water-assisted diffusional phase transitions in inorganic metal halide perovskites.

The stability of perovskite materials is profoundly influenced by the presence of moisture in the surrounding environment. While it is well-established that water triggers and accelerates the black-yellow phase transition, leading to the degradation of the photovoltaic properties of perovskites, the underlying microscopic mechanism remains elusive. In this study, we employ classical molecular dynamics simulations to examine the role of water molecules in the yellow-black phase transition in a typical inorganic metal halide perovskite, CsPbI3.

Cysteine-induced growth of jagged gold bipyramids from penta-twinned nanorod seeds.

The understanding on the growth mechanism of complex gold nanostructures both experimentally and theoretically can guide their design and fabrication toward various applications. In this work, we report a cysteine-directed overgrowth of penta-twinned nanorod seeds into jagged gold bipyramids with discontinuous stepped {hhk} facets. By monitoring the growth process, we find that {hhk} facets with large k/h values (∼7) are formed first at two ends of the nanorods, followed by the protrusion of the middle section exposing {hhk} facets with smaller indices (k/h ∼ 2-3).

Scaling Solute-Solvent Distances to Improve Solubility and Ion Paring Predictions in Rigid Ion Models.

Force fields based on the rigid ion model (RIM) have been developed to accurately predict the various physical and chemical properties of salts and water. However, the combined use of these models often fails to accurately predict the solubility of salts in water. To address this issue, several approaches, such as charge scaling or reparameterization, have been proposed.

Anisotropy in Near-Spherical Colloidal Nanoparticles.

Two major aspects of functional colloidal nanoparticles are their colloidal stability (dispersion) and controlled assembly of nanoparticles into ordered structures. Simplifying colloidal nanoparticles as isotropically interacting spheres is unsuitable for small nanoparticles capped with hydrocarbon chain ligands in which the ligand-ligand interaction plays a prominent role in the assembly processes. However, experimentally characterizing the ligand shell structure in solution presents significant challenges, and computer simulations yield divergent results without effective validation.

Dual Atomic Coherence in the Self-Assembly of Patchy Heterostructural Nanocrystals.

Advances in the synthesis and self-assembly of nanocrystals have enabled researchers to create a plethora of different nanoparticle superlattices. But while many superlattices with complex types of translational order have been realized, rotational order of nanoparticle building blocks within the lattice is more difficult to achieve. Self-assembled superstructures with atomically coherent nanocrystal lattices, which are desirable due to their exceptional electronic and optical properties, have been fabricated only for a few selected systems.

Controlling Nanoparticle Orientations in the Self-Assembly of Patchy Quantum Dot-Gold Heterostructural Nanocrystals.

Self-assembly of nanocrystals is a promising route for creating macroscale materials that derive function from the properties of their nanoscale building blocks. While much progress has been made assembling nanocrystals into different superlattices, controlling the relative orientations of nanocrystals in those lattices remains a challenge. Here, we combine experiments with computer simulations to study the self-assembly of patchy heterostructural nanocrystals (HNCs), consisting of near-spherical quantum dots decorated with regular arrangements of small gold satellites, into close-packed superlattices with pronounced orientational alignment of HNCs.

Orientational Order in Self-Assembled Nanocrystal Superlattices.

Self-assembly of nanocrystals into functional materials requires precise control over nanoparticle interactions in solution that are dominated by organic ligands that densely cover the surface of nanocrystals. Recent experiments have demonstrated that small truncated-octahedral nanocrystals can self-assemble into a range of superstructures with different translational and orientational order of nanocrystals. The origin of this structural diversity remains unclear.

Self-Assembly of Quantum Dot-Gold Heterodimer Nanocrystals with Orientational Order.

The self-assembly of nanocrystals into ordered superlattices is a powerful strategy for the production of functional nanomaterials. The assembly of well-ordered target structures, however, requires control over the building blocks' size and shape as well as their interactions. While nanocrystals with homogeneous composition are now routinely synthesized with high precision and assembled into various ordered structures, high-quality multicomponent nanocrystals and their ordered assemblies are rarely reported.

Atomistic understanding of cation exchange in PbS nanocrystals using simulations with pseudoligands.

Cation exchange is a powerful tool for the synthesis of nanostructures such as core-shell nanocrystals, however, the underlying mechanism is poorly understood. Interactions of cations with ligands and solvent molecules are systematically ignored in simulations. Here, we introduce the concept of pseudoligands to incorporate cation-ligand-solvent interactions in molecular dynamics.

A transferable force field for CdS-CdSe-PbS-PbSe solid systems.

A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al.

Heat-induced transformation of CdSe-CdS-ZnS core-multishell quantum dots by Zn diffusion into inner layers.

In this work, we investigate the thermal evolution of CdSe-CdS-ZnS core-multishell quantum dots (QDs) in situ using transmission electron microscopy (TEM). Starting at a temperature of approximately 250 °C, Zn diffusion into inner layers takes place together with simultaneous evaporation of particularly Cd and S. As a result of this transformation, CdxZn1-xSe-CdyZn1-yS core-shell QDs are obtained.

Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth.

Here, we show a novel solid-solid-vapor (SSV) growth mechanism whereby epitaxial growth of heterogeneous semiconductor nanowires takes place by evaporation-induced cation exchange. During heating of PbSe-CdSe nanodumbbells inside a transmission electron microscope (TEM), we observed that PbSe nanocrystals grew epitaxially at the expense of CdSe nanodomains driven by evaporation of Cd. Analysis of atomic-resolution TEM observations and detailed atomistic simulations reveals that the growth process is mediated by vacancies.

Core-shell reconfiguration through thermal annealing in Fe(x)O/CoFe2O4 ordered 2D nanocrystal arrays.

A great variety of single- and multi-component nanocrystals (NCs) can now be synthesized and integrated into nanocrystal superlattices. However, the thermal and temporal stability of these superstructures and their components can be a limiting factor for their application as functional devices. On the other hand, temperature induced reconstructions can also reveal opportunities to manipulate properties and access new types of nanostructures.

From sphere to multipod: thermally induced transitions of CdSe nanocrystals studied by molecular dynamics simulations.

Molecular dynamics (MD) simulations are used to show that a spherical zinc blende (ZB) nanocrystal (NC) can transform into a tetrapod or an octapod as a result of heating, by a local zincblende-to-wurtzite phase transformation taking place in the NC. The partial sphere-to-tetrapod or sphere-to-octapod transition occurs within simulation times of 30 ns and depends on both temperature and NC size. Surprisingly, the wurtzite (WZ) subdomains are not formed through a slip mechanism but are mediated by the formation of highly mobile Cd vacancies on the ZB{111} Cd atomic planes.