Liquid/Solid Surface-01

目录

• Liquid/Solid Surface-01
• Some Slip Model
• PE/Au
• PE/mica
• Oscillatory Couette flows
• Some United-Atom PE Force Field
• Details of the n-alkanes model
• The well-known (Siepmann-Karaborni-Smit) SKS united-atom potential model
• Capaldi et al.
• Bolten et al.

Liquid/Solid Surface-01

• Polyethylene(PE)

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	$U_{stretching}=\dfrac{k_{str}}{2}(l-l_{eq})^2$Ustretching​=2kstr​​(l−leq​)2	$k_{str}/k_B=452900 \ K/\mathring{A}^2$kstr​/kB​=452900 K/A˚2 $l_{eq}=1.54 \ \mathring{A}$leq​=1.54 A˚
Bending	$U_{bending}=\dfrac{k_{ben}}{2}(\theta-\theta_{eq})^2$Ubending​=2kben​​(θ−θeq​)2	$k_{ben}/k_B=62500 \ K/rad^2$kben​/kB​=62500 K/rad2 $\theta_{eq}=114^\circ$θeq​=114∘
Torsion	$U_{torsional}=\sum\limits_{m=0}^{3}a_mcos^m\phi$Utorsional​=m=0∑3​am​cosmϕ	$a_0/k_B=1010 \ K$a0​/kB​=1010 K, $a_1/k_B=2019 \ K$a1​/kB​=2019 K $a_2/k_B=136.4 \ K$a2​/kB​=136.4 K, $a_3/k_B=-3165 \ K$a3​/kB​=−3165 K
Non-bonded	$U_{lj}(r)=4\epsilon_{ij}[(\dfrac{\sigma_{ij}}{r})^{12}-(\dfrac{\sigma_{ij}}{r})^{6}]$Ulj​(r)=4ϵij​[(rσij​​)12−(rσij​​)6]	$CH_2: \epsilon/k_B=47 \ K, \sigma=3.93 \ \mathring{A}$CH2​:ϵ/kB​=47 K,σ=3.93 A˚ $CH_3: \epsilon/k_B=114 \ K, \sigma=3.93 \ \mathring{A}$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：

$k_{str}=900 \ kcal/mol/ \mathring{A}^2$kstr​=900 kcal/mol/A˚2

$k_{bend}=124.2 \ kcal/mol/ \mathring{A}^2$kbend​=124.2 kcal/mol/A˚2

$a_0=2 \ kcal/mol, a_1=4.01 \ kcal/mol, a_2=0.271 \ kcal/mol, a_3=-6.29 \ kcal/mol$a0​=2 kcal/mol,a1​=4.01 kcal/mol,a2​=0.271 kcal/mol,a3​=−6.29 kcal/mol

$CH_2: \epsilon=0.0933 \ kcal/mol, CH_3: \epsilon=0.2265 \ kcal/mol$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 .