Molecular dynamics simulation of a graphite-supported copper nanocluster: thermodynamic properties and gas adsorption

Can graphene improve the thermal conductivity of copper nanofluids?

Copper (Cu) nanofluids (NFs) have attracted attention due to their high thermal conductivity, which has conferred a wide variety of applications. However, their high reactivity favors oxidation, corrosion and aggregation, leading them to lose their properties of interest. Copper capped by graphene (Cu@G) core@shell nanoparticles (NPs) have also attracted interest from the medical and industrial sectors because graphene can shield the Cu NPs from undesired phenomena. Additionally, they share some properties that expand the range of applications of Cu NFs. In this work, new Morse potentials are reported to reproduce the behavior of Cu@G NPs through molecular dynamics. Coordination-dependent Morse parameters were fitted for C, H, and Cu based on density functional theory calculations. Then, these parameters were implemented to evaluate the thermal conductivity of Cu@G NFs employing the Green-Kubo formalism, with NPs from 1.5 to 6.1 nm at 100 to 800 K, varying the size, the number of layers and the orientation of the graphene flakes. It was found that Cu@G NFs are stable and have an improved thermal conductivity compared to the Cu NFs, being 3.7 to 18.2 times higher at 300 K with only one graphene layer and above 26.2 times higher for the graphene-trilayered NPs. These values can be higher for temperatures below 300 K. Oppositely, the size, homogeneity and orientations of the graphene flakes did not affect the thermal conductivity of the Cu@G NFs.

Structure and Thermodynamics of Metal Clusters on Atomically Smooth Substrates

We analyze the structure of model Ni_N and Cu_N clusters (N = 55, 147) supported on a variety of atomically smooth van der Waals surfaces. The global minima are mapped in the space of two parameters: (i) the laterally averaged surface stickiness, γ, which controls the macroscopic wetting angle, and (ii) the surface microstructure, which produces more subtle but important templating via epitaxial stresses. We find that adjusting the substrate lattice (even at constant γ) can favor different crystal plane orientations in the cluster, stabilize hexagonal close-packed order, or induce various defects, such as stacking faults, twin boundaries, and five-fold disclinations. Thermodynamic analysis reveals substrate-dependent solid-solid transitions in cluster morphology, with tunable transition temperature and sometimes exhibiting re-entrant behavior. These results shed new light on the extent to which a supporting surface can be used to influence the equilibrium behavior of nanoparticles.

Carbon monoxide adsorption on the single-walled carbon nanotube supported gold–silver nanoalloys

The carbon nanotube diameter and chirality have significant influences on CO adsorption.

Propene adsorption on gold–palladium nanoalloys supported on bundle nanotubes

Propene adsorption on (Pd–Au)_N nanoalloys supported on carbon nanotube (CNT) bundles has been investigated using molecular dynamics (MD) simulations at 300 K.

Abnormal change of melting points of gold nanoparticles confined between two-layer graphene nanosheets

A molecular dynamics simulation demonstrated that the melting temperature of gold nanoparticles confined in two-layer graphene nanosheets was indicated to decrease with nanoparticle size and a reasonable explanation is provided.

Properties of silver nanoclusters and bulk silver, using a new and accurate HFD-like potential, including many-body interactions: the inversion scheme and molecular dynamics simulation

A new potential function was obtained for silver nanoclusters and bulk silver via the inversion of viscosity collision integrals of monatomic silver vapor.

Molecular dynamics simulation of the deposition process of cold Ag-clusters under different landing conditions

We present a series of molecular dynamics simulations on the surface deposition process of initially free silver clusters (Agn) with different sizes (n = 100-2000) and morphologies. During the whole deposition process the morphology of the clusters was studied as a function of the landing conditions. These conditions include variations of the depth and range of the substrate potential as well as the thermal coupling to the surface and a variation of the impact velocity of the free clusters. Depending on the applied conditions the clusters' final form ranges from spread out fragments via deformed and restructured heaps to quasi unchanged spherical clusters sitting at the surface. Under certain landing conditions larger clusters retain their initial multiply twinned morphology upon deposition, while smaller ones undergo structural transitions to form single domain particles. Furthermore, the occurrence of a structural transition depends on the initial structure-initially decahedral clusters tend to conserve their morphology better than icosahedral ones. The same behavior can also be observed in our experiments, where silver clusters were grown in helium nanodroplets and subsequently deposited on amorphous carbon substrates.

Investigation of thermal evolution of copper nanoclusters encapsulated in carbon nanotubes: a molecular dynamics study

We have simulated the heating and cooling processes of Cu_N nanoclusters encapsulated in CNTs with different diameters and chiralities.