scholarly journals Molecular dynamics simulation of entanglement spreading in generalized hydrodynamics

2020 ◽  
Vol 8 (4) ◽  
Author(s):  
Márton Mestyán ◽  
Vincenzo Alba
Keyword(s):  
Molecular Dynamics ◽  
Scaling Limit ◽  
Dynamics Simulation ◽  
Full Time ◽  
Large Space ◽  
Time Dynamics ◽  
Generalized Hydrodynamics ◽  
Analytical Results ◽  
Xxz Chain ◽  
Quantum Quenches

We consider a molecular dynamics method, the so-called flea gas for computing the evolution of entanglement after inhomogeneous quantum quenches in an integrable quantum system. In such systems the evolution of local observables is described at large space-time scales by the Generalized Hydrodynamics approach, which is based on the presence of stable, ballistically propagating quasiparticles. Recently it was shown that the GHD approach can be joined with the quasiparticle picture of entanglement evolution, providing results for entanglement growth after inhomogeneous quenches. Here we apply the flea gas simulation of GHD to obtain numerical results for entanglement growth. We implement the flea gas dynamics for the gapped anisotropic Heisenberg XXZ spin chain, considering quenches from globally homogeneous and piecewise homogeneous initial states. While the flea gas method applied to the XXZ chain is not exact even in the scaling limit (in contrast to the Lieb-Liniger model), it yields a very good approximation of analytical results for entanglement growth in the cases considered. Furthermore, we obtain the full-time dynamics of the mutual information after quenches from inhomogeneous settings, for which no analytical results are available.

scholarly journals A Path Integral Molecular Dynamics Simulation of a Harpoon-Type Redox Reaction in a Helium Nanodroplet

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5783
Author(s):  
Alvaro Castillo-García ◽  
Andreas W. Hauser ◽  
María Pilar de Lara-Castells ◽  
Pablo Villarreal
Keyword(s):  
Molecular Dynamics ◽  
Electron Transfer ◽  
Long Range ◽  
Path Integral ◽  
Chem Phys ◽  
Dynamics Simulation ◽  
Ionization Mass ◽  
Implicit Assumption ◽  
Time Dynamics ◽  
The Impact

We present path integral molecular dynamics (PIMD) calculations of an electron transfer from a heliophobic Cs2 dimer in its (3Σu) state, located on the surface of a He droplet, to a heliophilic, fully immersed C60 molecule. Supported by electron ionization mass spectroscopy measurements (Renzler et al., J. Chem. Phys.2016, 145, 181101), this spatially quenched reaction was characterized as a harpoon-type or long-range electron transfer in a previous high-level ab initio study (de Lara-Castells et al., J. Phys. Chem. Lett.2017, 8, 4284). To go beyond the static approach, classical and quantum PIMD simulations are performed at 2 K, slightly below the critical temperature for helium superfluidity (2.172 K). Calculations are executed in the NVT ensemble as well as the NVE ensemble to provide insights into real-time dynamics. A droplet size of 2090 atoms is assumed to study the impact of spatial hindrance on reactivity. By changing the number of beads in the PIMD simulations, the impact of quantization can be studied in greater detail and without an implicit assumption of superfluidity. We find that the reaction probability increases with higher levels of quantization. Our findings confirm earlier, static predictions of a rotational motion of the Cs2 dimer upon reacting with the fullerene, involving a substantial displacement of helium. However, it also raises the new question of whether the interacting species are driven out-of-equilibrium after impurity uptake, since reactivity is strongly quenched if a full thermal equilibration is assumed. More generally, our work points towards a novel mechanism for long-range electron transfer through an interplay between nuclear quantum delocalization within the confining medium and delocalized electronic dispersion forces acting on the two reactants.

scholarly journals Study on Lubrication Characteristics of C4-Alkane and Nanoparticle during Boundary Friction by Molecular Dynamics Simulation

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1464
Author(s):  
Xuan Zheng ◽  
Lihong Su ◽  
Guanyu Deng ◽  
Jie Zhang ◽  
Hongtao Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Sliding Friction ◽  
Early Stage ◽  
Normal Load ◽  
Dynamics Simulation ◽  
Boundary Friction ◽  
Nonequilibrium Molecular Dynamics ◽  
Large Space ◽  
Friction Mode ◽  
Contact Surfaces

Lubricant has been widely applied to reduce wear and friction between the contact surfaces when they are in relative motion. In the current study, a nonequilibrium molecular dynamics (NEMD) simulation was specifically established to conduct a comprehensive investigation on the dynamic contact between two iron surfaces in a boundary friction system considering the mixed C4-alkane and nanoparticles as lubricant. The main research objective was to explore the effects of fluid and nanoparticles addition on the surface contact and friction force. It was found that nanoparticles acted like ball bearings between the contact surfaces, leading to a change of sliding friction mode to rolling friction mode. Under normal loads, plastic deformation occurred at the top surface because nanoparticles were mainly supporting the normal load. By increasing the number of C4-alkane molecules between two contact surfaces, the contact condition has been changed from partial to full lubrication. In addition, an attractive force from the solid–liquid LJ interaction between C4-alkane and surfaces was observed at the early stage of sliding, due to the large space formed by wall surfaces and nanoparticles. The findings in this paper would be beneficial for understanding the frictional behavior of a simple lubricant with or without nanoparticles addition in a small confinement.

Sign in / Sign up

Export Citation Format

Share Document