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Title: Computational simulations of solvation force and squeezing out of dodecane chain molecules in an atomic force microscope

Abstract

Understanding the squeeze out behaviors of liquid films at nanometer scale in an atomic force microscope (AFM) has been a significant interest since the 1990s. We carry out all-atom static-mode AFM simulations in a liquid-vapor molecular dynamics ensemble to investigate the solvation force oscillation and squeeze out mechanisms of a confined linear dodecane fluid between a gold AFM tip and a mica substrate. Solvation force oscillations are found to be associated with the layering transition of the liquid film and unstable jumps of the AFM tip. Detailed structural analyses and molecular animations show that the local permeation of chain molecules and the squeeze out of molecules near the edge of contact promote the layering transition under compression. The confinement-induced slow down dynamics is manifested by the decrease in diffusivity and increase in rotational relaxation times. Furthermore, the persistent diffusive behavior of dodecane chain molecules even in the single-monolayer film is attributed to the chain sliding motions in the film due to the substantial vacancy space and thermal fluctuations.

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1]
  1. The George Washington University, Washington, DC (United States). Dept. of Mechanical and Aerospace Engineering
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE
OSTI Identifier:
1497878
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 147; Journal Issue: 5; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Xu, Rong -Guang, Xiang, Yuan, and Leng, Yongsheng. Computational simulations of solvation force and squeezing out of dodecane chain molecules in an atomic force microscope. United States: N. p., 2017. Web. doi:10.1063/1.4996886.
Xu, Rong -Guang, Xiang, Yuan, & Leng, Yongsheng. Computational simulations of solvation force and squeezing out of dodecane chain molecules in an atomic force microscope. United States. doi:10.1063/1.4996886.
Xu, Rong -Guang, Xiang, Yuan, and Leng, Yongsheng. Mon . "Computational simulations of solvation force and squeezing out of dodecane chain molecules in an atomic force microscope". United States. doi:10.1063/1.4996886. https://www.osti.gov/servlets/purl/1497878.
@article{osti_1497878,
title = {Computational simulations of solvation force and squeezing out of dodecane chain molecules in an atomic force microscope},
author = {Xu, Rong -Guang and Xiang, Yuan and Leng, Yongsheng},
abstractNote = {Understanding the squeeze out behaviors of liquid films at nanometer scale in an atomic force microscope (AFM) has been a significant interest since the 1990s. We carry out all-atom static-mode AFM simulations in a liquid-vapor molecular dynamics ensemble to investigate the solvation force oscillation and squeeze out mechanisms of a confined linear dodecane fluid between a gold AFM tip and a mica substrate. Solvation force oscillations are found to be associated with the layering transition of the liquid film and unstable jumps of the AFM tip. Detailed structural analyses and molecular animations show that the local permeation of chain molecules and the squeeze out of molecules near the edge of contact promote the layering transition under compression. The confinement-induced slow down dynamics is manifested by the decrease in diffusivity and increase in rotational relaxation times. Furthermore, the persistent diffusive behavior of dodecane chain molecules even in the single-monolayer film is attributed to the chain sliding motions in the film due to the substantial vacancy space and thermal fluctuations.},
doi = {10.1063/1.4996886},
journal = {Journal of Chemical Physics},
number = 5,
volume = 147,
place = {United States},
year = {2017},
month = {8}
}

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Works referenced in this record:

UFF, a full periodic table force field for molecular mechanics and molecular dynamics simulations
journal, December 1992

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