临界点附近CO<sub>2</sub>物性畸变特性的分子动力学研究

唐佳; 黄彦平; 王俊峰; 臧金光; 刘光旭; 刘睿龙

doi:10.13832/j.jnpe.2021.04.0073

临界点附近CO₂物性畸变特性的分子动力学研究

doi: 10.13832/j.jnpe.2021.04.0073

中国核动力研究设计院中核核反应堆热工水力技术重点实验室，成都， 610213

基金项目: 国家自然科学基金核技术创新联合基金项目（U1867218）

详细信息

作者简介:
唐　佳（1991—），男，博士研究生，现主要从事超临界二氧化碳物性及工程应用方面的研究，E-mail: 164692715@qq.com

通讯作者:
黄彦平，E-mail: hyanping007@163.com

中图分类号: TL339； O552
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出版历程
- 收稿日期: 2020-05-10
- 修回日期: 2020-12-20
- 刊出日期: 2021-08-15

Study on Molecular Dynamics of Singular Nature of Physical Properties near Critical Point in Carbon Dioxide System

CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China, Chengdu, 610213, China

摘要

摘要: 通过分子动力学模拟方法，从微观角度研究了临界点附近CO₂物性畸变特性。分子动力学模拟表明COMPASS力场在远离临界点时具有较高精度，在临界点附近精度较低但可反映密度畸变现象。通过划分模拟空间，获得体系密度涨落特性，分析表明，临界点附近存在很大的密度涨落，且临界点前后密度涨落值呈现不对称特性；在CO₂分子上建立局部坐标，并定义了二聚体构型三参数描述方法，该描述方法能够全面描述二聚体构型分布，模拟结果显示在平行构型、T构型及十字构型中，T构型出现概率最高，3种构型的转变与物性畸变或存在紧密关联。
- 超临界二氧化碳 /
- 物性畸变 /
- 微观特性 /
- 分子动力学模拟
Abstract: Based on the molecular dynamics simulations, this paper analyzed the singular nature of physical properties of the carbon dioxide near the critical point. Detailed analysis of density simulation exhibited that an excellent agreement can be obtained by COMPASS forcefield besides the pseudo-critical region, while the peculiar behavior of density can again be observed. The computational domain is divided into the small sub-domains in which the standard deviation are evaluated as density fluctuation, and it shows maximum near the critical point and higher values at supercritical condition than that at subcritical condition. A new 3-parameter model was put forward to define the CO₂ dimer distribution after each molecule in the domain had been supplied with the local coordination frame. The result shows that the T-shaped dimer is with higher probability to be formed than the parallel and crossed configuration, and the conversion of these dimer conformations closely associates with the peculiar properties of the critical point.
- Supercritical carbon dioxide /
- Peculiar physical properties /
- Microscopic characteristics /
- Molecular dynamics simulation

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图 1 密度模拟路径

Figure 1. Simulation Route of Density Simulation

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图 2 路径①模拟情况

Figure 2. Simulation Result of Route NO. 1

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图 3 路径②模拟情况

Figure 3. Simulation Result of Route No. 2

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图 4 路径③模拟情况

Figure 4. Simulation Result of Route No. 3

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图 5 路径③模拟情况(相对偏差)

Figure 5. Simulation Result of Route No. 3 (Relative Deviation)　　　　　

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图 6 沿临界压力p =7.38 MPa等压线温度变化时的密度涨落　　　　　

Figure 6. Density Fluctuation Variation for Different Temperature with Fixed Pressure (7.38 MPa)

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图 7 常见的二氧化碳二聚体构型

Figure 7. CO₂ Dimer Structure

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图 8 文献[14]遗漏二聚体构型

Figure 8. Unforeseen CO₂ Dimer Structure in REF.[14]

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图 9 CO₂二聚体构型在三维空间的概率分布

Figure 9. Distribution in 3D Space of CO₂ Dimer Structure

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图 10 CO₂ 3种二聚体构型分布概率情况

Figure 10. Distribution Probability of CO₂ Dimer Structure

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参考文献(27)

[1]	NOWAK P, TIELKES T H, KLEINRAHM R, et al. Supplementary measurements of the (p, ρ, T) relation of carbon dioxide in the homogeneous region at T=313K and on the coexistence curve at T=304 K[J]. J. Chem. Thermodynamics, 1997(29): 885-889. doi: 10.1006/jcht.1997.0208
[2]	TOM K S. The feasibility of using supercritical carbon dioxide as a coolant for the CANDU reactor[D]. Canada: Master Thesis of University of British Columbia, 1978.
[3]	黄彦平,王俊峰. 超临界二氧化碳在核反应堆系统中的应用[J]. 核动力工程,2012, 33(3): 21-27. doi: 10.3969/j.issn.0258-0926.2012.03.005
[4]	黄彦平,刘光旭,王俊峰,等. 加热工况下圆管内超临界二氧化碳传热关系式分析评价[J]. 核动力工程,2014, 35(3): 1-5.
[5]	黄彦平,刘生晖,刘光旭,等. 典型超临界二氧化碳强迫对流传热关联式评价分析[J]. 核动力工程,2016, 37(1): 28-33.
[6]	ANDREWS T. The Bakerian lecture: on the continuity of the gaseous and liquid states of matter[J]. Philosophical Transactions of the Royal Society, 1869(159): 575-590. doi: 10.1098/rstl.1869.0021
[7]	VAN DER WAALS J D. Over de continuiteit van den Gas-en Vloeistoftoestand[D]. Leiden: Leiden University, 1873.
[8]	于渌, 郝柏林, 陈晓松. 边缘奇迹: 相变和临界现象[M]. 北京: 科学出版社, 2005.
[9]	TSUDA S I, TOMI M, TSUBOI N, et al. Extraction of the density fluctuation in diatomic fluids around the critical points using molecular dynamics simulation[J]. Journal of Nanoscience and Nanotechnology, 2015(15): 3117-3120. doi: 10.1166/jnn.2015.9623
[10]	苑世领, 张恒, 张冬菊. 分子模拟-理论与实验[M]. 北京: 化学工业出版社, 2016: 2, 48.
[11]	UEDA K, KOMAI T, YU I, et al. Molecular dynamics study on the density fluctuation of supercritical water[J]. J. Comput. Chem, Jpn, 2002, 1(3): 83-88. doi: 10.2477/jccj.1.83
[12]	何岩. 超临界CO₂体系的扩散性质和微观结构的分子动力学研究[D]. 天津: 天津大学, 2007.
[13]	ANGUS S, ARMSTRONG B, REUCK K M. Carbon Dioxide: International thermodynamics tables of the fluid state-3[M]. New York: Pergamon Press, 1976: 78-79, 298-359.
[14]	张阳. 分子模拟在纯超临界流体及其二元混合物体系中的应用[D]. 北京: 清华大学, 2005: 30-45.
[15]	SUN H. COMPASS: An ab Initio force-field optimized for condensed-phase applications-overview with details on Alkane and Benzene compounds[J]. J. Phys. Chem. B, 1998, 102(38): 7338-7364. doi: 10.1021/jp980939v
[16]	SUN H, REN P, FRIED J R. The COMPASS forcefield: parameterization and validation for poly phosphazenes[J]. Comput. Theor. Polym. Sci., 1998, 8(1/2): 229-246.
[17]	严六明, 朱素华. 分子动力学模拟的理论与实践[M]. 北京: 科学出版社, 2013.
[18]	IWAI Y, HIGASHI H, UCHIDA H, et al. Molecular dynamics simulation of diffusion coefficients of naphthalene and 2-naphthol in supercritical carbon dioxide[J]. Fluid Phase Equilib, 1997(127): 251-261. doi: 10.1016/S0378-3812(96)03139-1
[19]	严六明,严琪良,刘洪来,等. 模型溶液的分子动力学模拟及扩散系数计算[J]. 华东理工大学学报,1997, 23(4): 477-483.
[20]	INOMATA H, SAITO S, DEBENDE P A, et al. Molecular dynamics simulation of infinitely dilute solutions of benzene in supercritical CO₂[J]. Fluid Phase Equilib., 1996(116): 282-288. doi: 10.1016/0378-3812(95)02897-8
[21]	HIGASHI H, IWAI Y, ARAI Y. Calculation of self-diffusion and trafer diffusion coefficients near critical point of carbon dioxide using molecular dynamics[J]. Ind. Eng. Chems. Res., 2000(39): 4567-4570. doi: 10.1021/ie000173x
[22]	周健,陆小华,王延如,等. 有机物在超临界 CO2中的无限稀释扩散系数的分子动力学模拟[J]. 化工学报,1999, 50(4): 491-499. doi: 10.3321/j.issn:0438-1157.1999.04.009
[23]	NIST, Standard Reference Database 23[S]. Version 9.0.
[24]	YOON T J, HA M Y, LEE W B, et al. Monte Carlo simulations on the local density inhomogeneities of sub-and supercritical carbon dioxide: statistical analysis based on the voronoi tessellation[J]. The Journal of Supercritical Fluids, 2017(119): 36-43.
[25]	林宗涵. 热力学与统计物理学[M]. 北京: 北京大学出版社, 2018: 352.
[26]	KOLAFA J, NEZBEDA I, LISAL M. Effect of short- and long-range forces on the properties of fluids. III. Dipolar and quadrupolar fluids[J]. Mol. Phys. 2001 (99): 1751-1764.
[27]	FEDCHENIA I I, SCHRODER J. Local orientational correlations and short time anisotropic motion in molecular liquids: computer simulation of liquid CO₂[J]. J. Chem. Phys. 1997(106): 7749-7755.