The method for determining nano-contact angle

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	The method for determining nano-contact angle
	Cui SW(崔树稳); Zhu RC(朱如曾); Wei JA(魏久安); Wang XS(王小松); Yang HX(杨洪秀); Xu SH(徐升华); Sun ZW(孙祉伟)
刊名	物理学报=Acta Physica Sinica
	2015-06-05
通讯作者邮箱	Zhurz@lnm.imech.ac.cn
卷号	64 期号:11 页码:116802
关键词	nano-contact angle molecular dynamics simulation surface tension practical formula
ISSN号	1000-3290
通讯作者	Zhu, RZ (reprint author), Chinese Acad Sci, Inst Mech, State Key Lab Nonlinear Mech, Beijing 100190, Peoples R China.
产权排序	[Cui Shu-Wen] Normal Univ, Dept Phys & Elect Informat, Cangzhou 061001, Peoples R China; [Zhu Ru-Zeng] Chinese Acad Sci, Inst Mech, State Key Lab Nonlinear Mech, Beijing 100190, Peoples R China; [Wei Jiu-An] Silfex, Eaton, OH 45320 USA; [Wang Xiao-Song] Henan Polytech Univ, Inst Mech & Power Engn, Jiaozuo 454003, Peoples R China; [Yang Hong-Xiu] CangZhou Normal Univ, CangZhou Normal Univ Lib, Cangzhou 061001, Peoples R China; [Zhu Ru-Zeng; Xu Sheng-Hua; Sun Zhi-Wei] Chinese Acad Sci, Inst Mech, Key Lab Micrograv, Beijing 100190, Peoples R China
中文摘要	Theoretical analyses are given to the known approaches of nano-contact angle and arrive at the conclusions: 1) All the approaches based on the assumptions of Qusi-uniform liquid film, or uniform liquid molecular density, or uniform liquid molecular densities respectively inside and outside the interface layer cannot give the correct nano-contact angle, and it is difficult to improve them. Among these approaches, both the conclusions of nano-contact angle sure being 0 degrees and sure being 180 degrees are false. 2) Density functional theory (DFT) approach and Molecular Dynamics (MD) approach are capable to treat of nano-contact angle, however, the work is very heavy for using the DFT approach. 3) In 1995, Ruzeng Zhu (College Physic [Vol. 14 (2), p1-4 (in Chinese)], corrected the concept of contact angle in a earlier false theory for macro contact angle and obtained the most simple and convenient approximate formula of nano-contact angle alpha = (1 - 2 E-PS/E-PL) pi, where E-PL is the potential of a liquid molecule in the internal liquid and E-PS is the interact potential between a liquid molecule and the solid on which it locats. Both E-PS and E-PL can be obtained by MD, therefore this theory as a approximate simplified form belongs to Molecular Dynamics approach of nano-contact angle. The results of 0 degrees and 180 degrees for complete wetting and complete non-wetting given by this formula are correct under the assumption of incompressible fluid, therefore, this theory is worthy of further development. For this end, based on the physical analysis, we assume that the potential energy of a liquid molecule on the Gibss surface of tension outside the three-phase contact area is E-PL/2x and that of a liquid molecule on the three-phase contact line is (1 + kE(PS)/E-PL) alpha E-PL/2x pi, where x and k are optimal parameters. According to the condition that the potential energy is the same everywhere on the Gibss surface of tension, an improved approximate formula for nano-contact angle alpha = pi(1 - 2xE(PS)/E-PL)/(1 + kE(PS)/E-PL) is obtained. To obtain the value of x and k, MD simulations are carried on argon liquid cylinders placed on the solid surface under the temperature 90 K, by using the lennard - Jones (LJ) potentials for the interaction between liquid molecules and for that between a liquid molecule and a solid molecule with the variable coefficient of strength a. Eight values of a between 0.650 and 0.825 are used. The Gibss surfaces of tension are obtained by simulations and their bottom angles are treated as the approximate nano-contact angles. Combining these data with the physical conditions (when E-PS/E-PL = 0, alpha = pi), the optimized parameter values x = 0.7141, k = 1.6051 with the correlation coefficient 0.9997 are obtained by least square method. This correlation coefficient close enough to 1 indicates that for nano liquid solid contact system with different interaction strength, the parameter of optimization x and k really can be viewed as constants, so that our using MD simulation to determine of the optimized parameters is feasible and our approximate formula is of general applicability.
类目[WOS]	Physics, Multidisciplinary
研究领域[WOS]	Physics
收录类别	SCI ; EI ; CSCD
原文出处	Zhu, RZ (reprint author), Chinese Acad Sci, Inst Mech, State Key Lab Nonlinear Mech, Beijing 100190, Peoples R China.Theoretical analyses are given to the known approaches of nano-contact angle and arrive at the conclusions: 1) All the approaches based on the assumptions of Qusi-uniform liquid film, or uniform liquid molecular density, or uniform liquid molecular densities respectively inside and outside the interface layer cannot give the correct nano-contact angle, and it is difficult to improve them. Among these approaches, both the conclusions of nano-contact angle sure being 0 degrees and sure being 180 degrees are false. 2) Density functional theory (DFT) approach and Molecular Dynamics (MD) approach are capable to treat of nano-contact angle, however, the work is very heavy for using the DFT approach. 3) In 1995, Ruzeng Zhu (College Physic [Vol. 14 (2), p1-4 (in Chinese)], corrected the concept of contact angle in a earlier false theory for macro contact angle and obtained the most simple and convenient approximate formula of nano-contact angle alpha = (1 - 2 E-PS/E-PL) pi, where E-PL is the potential of a liquid molecule in the internal liquid and E-PS is the interact potential between a liquid molecule and the solid on which it locats. Both E-PS and E-PL can be obtained by MD, therefore this theory as a approximate simplified form belongs to Molecular Dynamics approach of nano-contact angle. The results of 0 degrees and 180 degrees for complete wetting and complete non-wetting given by this formula are correct under the assumption of incompressible fluid, therefore, this theory is worthy of further development. For this end, based on the physical analysis, we assume that the potential energy of a liquid molecule on the Gibss surface of tension outside the three-phase contact area is E-PL/2x and that of a liquid molecule on the three-phase contact line is (1 + kE(PS)/E-PL) alpha E-PL/2x pi, where x and k are optimal parameters. According to the condition that the potential energy is the same everywhere on the Gibss surface of tension, an improved approximate formula for nano-contact angle alpha = pi(1 - 2xE(PS)/E-PL)/(1 + kE(PS)/E-PL) is obtained. To obtain the value of x and k, MD simulations are carried on argon liquid cylinders placed on the solid surface under the temperature 90 K, by using the lennard - Jones (LJ) potentials for the interaction between liquid molecules and for that between a liquid molecule and a solid molecule with the variable coefficient of strength a. Eight values of a between 0.650 and 0.825 are used. The Gibss surfaces of tension are obtained by simulations and their bottom angles are treated as the approximate nano-contact angles. Combining these data with the physical conditions (when E-PS/E-PL = 0, alpha = pi), the optimized parameter values x = 0.7141, k = 1.6051 with the correlation coefficient 0.9997 are obtained by least square method. This correlation coefficient close enough to 1 indicates that for nano liquid solid contact system with different interaction strength, the parameter of optimization x and k really can be viewed as constants, so that our using MD simulation to determine of the optimized parameters is feasible and our approximate formula is of general applicability.
语种	中文
CSCD记录号	CSCD:5439496
WOS记录号	WOS:000355695600044
内容类型	期刊论文
源URL	[http://dspace.imech.ac.cn/handle/311007/54966]
专题	力学研究所_非线性力学国家重点实验室力学研究所_国家微重力实验室
推荐引用方式 GB/T 7714	Cui SW,Zhu RC,Wei JA,et al. The method for determining nano-contact angle[J]. 物理学报=Acta Physica Sinica,2015,64(11):116802.
APA	崔树稳.,朱如曾.,魏久安.,王小松.,杨洪秀.,...&孙祉伟.(2015).The method for determining nano-contact angle.物理学报=Acta Physica Sinica,64(11),116802.
MLA	崔树稳,et al."The method for determining nano-contact angle".物理学报=Acta Physica Sinica 64.11(2015):116802.