Liquid/Solid Surface-01
Some Slip Model
PE/Au
Atomistic representations of the PE/Au system at equilibrium (left) and under constant Couette flow (right).
Sgouros AP, Theodorou DN. Atomistic simulations of long-chain polyethylene melts flowing past gold surfaces: structure and wall-slip. Molecular Physics 2020:1–20. https://doi.org/10.1080/00268976.2019.1706775 .
PE/mica
Schematics for confined polymer melts.
Jeong S, Cho S, Kim JM, Baig C. Molecular mechanisms of interfacial slip for polymer melts under shear flow. J. Rheol. 2017;61(2):253–64. https://doi.org/10.1122/1.4974907 .
Oscillatory Couette flows
(Color online) Positions of fluid monomers (open blue circles) and wall atoms (filled gray circles). The upper wall oscillates with the angular frequency x in the ^x direction (indicated by the double-sided arrow), while the lower wall is always stationary
Priezjev NV. Molecular dynamics simulations of oscillatory Couette flows with slip boundary conditions. Microfluid Nanofluid 2013;14(1-2):225–33. https://doi.org/10.1007/s10404-012-1040-5 .
Some United-Atom PE Force Field
Details of the n-alkanes model
Siepmann JI, Karaborni S, Smit B. Simulating the critical behaviour of complex fluids. Nature 1993;365(6444):330–2. https://doi.org/10.1038/365330a0 .
The well-known (Siepmann-Karaborni-Smit) SKS united-atom potential model
INTERACTION |
form |
Parameter |
Strectch |
Ustretching=2kstr(l−leq)2 |
kstr/kB=452900 K/A˚2
leq=1.54 A˚ |
Bending |
Ubending=2kben(θ−θeq)2 |
kben/kB=62500 K/rad2
θeq=114∘ |
Torsion |
Utorsional=m=0∑3amcosmϕ |
a0/kB=1010 K,
a1/kB=2019 K
a2/kB=136.4 K,
a3/kB=−3165 K |
Non-bonded |
Ulj(r)=4ϵij[(rσij)12−(rσij)6] |
CH2:ϵ/kB=47 K,σ=3.93 A˚
CH3:ϵ/kB=114 K,σ=3.93 A˚ |
Baig C, Mavrantzas VG, Kröger M. Flow Effects on Melt Structure and Entanglement Network of Linear Polymers: Results from a Nonequilibrium Molecular Dynamics Simulation Study of a Polyethylene Melt in Steady Shear. Macromolecules 2010;43(16):6886–902. https://doi.org/10.1021/ma100826u .
这篇论文描述的参数并不能直接输入至LAMMPS里,需要进行一下单位换算,推荐一个 单位转换工具,换算后的结果如下:
kstr=900 kcal/mol/A˚2
kbend=124.2 kcal/mol/A˚2
a0=2 kcal/mol,a1=4.01 kcal/mol,a2=0.271 kcal/mol,a3=−6.29 kcal/mol
CH2:ϵ=0.0933 kcal/mol,CH3:ϵ=0.2265 kcal/mol
Capaldi et al.
Capaldi FM, Boyce MC, Rutledge GC. Molecular response of a glassy polymer to active deformation. Polymer 2004;45(4):1391–9. https://doi.org/10.1016/j.polymer.2003.07.011 .
Bolten et al.
Ko MJ, Waheed N, Lavine MS, Rutledge GC. Characterization of polyethylene crystallization from an oriented melt by molecular dynamics simulation. J Chem Phys 2004;121(6):2823–32. https://doi.org/10.1063/1.1768515 .