Density dependent structural phase transition for confined copper: origin of the layering

Abstract

Confinement presents the opportunity for novel structural transition scenarios not observed in three-dimensional systems. Here, we report a comprehensive molecular dynamic (MD) study of the structural phase transition induced by density for an ordinary metal copper (Cu) confined between two parallel panel walls. At 4.19 g cm-3 < ρ < 4.66 g cm-3, a notable structural phase transition occurs between the triangle unit cell structure and quasi-square unit cell structure upon densification. Both the bond order parameter (BOP) and angular distribution function (ADF) can provide evidence for the transition. We highlight the fact that when the sole decrease of the atom distance cannot adapt to the further densification, the system starts to adjust the neighboring bond angle and promote the layering transition, thus inducing the structural phase transition. At the metastable coexistence zone, the viscosity exhibits a remarkable drop and the diffusion coefficient shows a notable increase, both facilitating the accomplishment of the structural transition. Our results will trigger more interest on the phase transition under confinement in a metallic system.

Atomistics of pre-nucleation layering of liquid metals at the interface with poor nucleants

“…Hence, the PNLs near the (0001) sapphire substrate endure tremendous resistance to becoming denser. According to the studies of Alert et al 20,40 and Duan et al 9 , atomic density plays a pivotal role in the formation of liquid layers. Therefore, the low atomic density of PNLs near the (0001) sapphire substrate caused by the large negative interfacial lattice mismatch hinders the further ordering of the PNL1.…”

“…Thermodynamic analysis of pre-nucleation liquid layering. Revealing the mechanism of pre-nucleation liquid layering is a long-standing issue 8,9,[44][45][46][47][48][49] . In the following, we will analyse the liquid layering in the perspective of interfacial thermodynamics.…”

“…Such nuclei may manifest as spherical caps when forming on foreign surfaces, which is termed as heterogeneous nucleation. Recently, this theory has been challenged by the observation of pre-nucleation layers (PNLs) adjacent to the atomically smooth solid surfaces [3][4][5][6][7][8][9][10] . Different from the nuclei described by the CNT, the PNLs are thermodynamically stable structures that normally appear at a temperature above the liquids (T 1 ) by spontaneous liquid layering, and the formation of the PNLs is believed to be an adsorption process.…”

Oriented Crystallization of Ammonium Sulfate from Hexagonal Boron Nitride/Sulfuric Acid Intercalation Compounds

“…This is analogous to the case of prenucleation layers that are created adjacent to the atomically smooth solid surface under confinement conditions. 12,28,29 The final growth orientation will be governed by the crystallographic direction of the basal crystal structure, which will be determined by the configuration and bonding environment of the intercalation species. It is probable that the structural environment of the intercalants is not uniform throughout the interlayer spaces.…”

Substrate-Induced Liquid Layering: A New Insight into the Heterogeneous Nucleation of Liquid Metals

“…According to the research of Duan et al [58], the increase of liquid atomic density is the origin of liquid layering. Duan et al's study highlights the influence of atomic density on the phase transformation in liquid, and is consistent with the landscape inversion phase transformation (LIPT) proposed by Alert and co-workers [59], which underlines the influence of particle density on the transformation of the in-plane structures of particles constrained on a periodic substrate.…”