Molecular rotation-caused autocorrelation behaviors of thermal noise in water

The finite autocorrelation time of thermal noise is crucial to unidirectional transportation on the molecular scale.Therefore,it is important to understand the cause of the intrinsic picosecond autocorrelation time of thermal noise in water.In this work,we use molecular dynamics simulations to compare the autocorrelation behaviors of the thermal noise,hydrogen bonds,and molecular rotations found in water.We found that the intrinsic picosecond autocorrelation time for thermal noise is caused by finite molecular rotation relaxation,in which hydrogen bonds play the role of a bridge.Furthermore,the simulation results show that our method of calculating the autocorrelation of thermal noise,by observing the fiuctuating force on an oxygen atom of water,provides additional information about molecular rotations.Our findings may advance the understanding of the anomalous dynamic nanoscale behavior of particles,and the applications of terahertz technology in measuring the structural and dynamical information of molecules in solutions.

Correlation between mixing enthalpy and structural order in liquid Mg−Si system

The mixing enthalpies and structural order in liquid Mg−Si system were investigated via ab-initio molecular dynamics at 1773 K.By calculating the transferred charges and electron density differences,the dominance of Si−Si interactions in the chemical environments around Si was demonstrated,which determined that the mixing enthalpy reached the minimum on Mg-rich side.In terms of Honeycutt and Anderson(HA)bond pairs based on the partial pair correlation functions,the attraction between Si−Si pairs and Mg atoms was revealed,and the evolution of structural order with Si content was characterized as a process of constituting frame structures by Si−Si pairs that dispersed Mg atoms.Focusing on tetrahedral order of local Si-configurations,a correlation between the mixing enthalpy and structural order was uncovered ultimately,which provided a new perspective combining the energetics with geometry to understand the liquid Mg−Si binary system.

First-principles calculations of solute–vacancy interactions in aluminum

The interactions of solute atoms with vacancies play a key role in diffusion and precipitation of alloying elements,ultimately influencing the mechanical properties of aluminum alloys.In this study,first-principles calculations are systematically performed to quantify the solute–vacancy interactions for the 3d–4p series and the 4d–5p series.The solute–vacancy interaction gradually transforms from repulsion to attraction from left to right.The solute–vacancy binding energy is sensitive to the supercell size for elements at the beginning.These behaviors of the solute–vacancy binding energy can be understood in terms of the combination and competition between the elastic and electronic interactions.Overall,the electronic binding energy follows a similar trend to the total binding energy and plays a major role in the solute–vacancy interactions.