N-脒基脲二硝酰胺盐晶体形貌的分子动力学研究

doi:10.7503/cjcu20170363

摘要/Abstract

摘要：

采用分子动力学方法, 在正侧(NVT)系综下研究了N-脒基脲二硝酰胺盐(FOX-12)在溶剂中的晶体形貌. 通过构建溶剂分子层-晶面的界面吸附模型模拟其动力学平衡构型, 计算溶剂与晶体表面间的结合能, 进而对真空附着能进行修正并获得溶剂条件下的晶貌. 使用自然冷却法在水和水/甲醇中培养FOX-12晶体并利用扫描电子显微镜进行了表征. 结果表明, 在真空条件下决定FOX-12晶貌的6个重要晶面为(110), (200), (201), (011), (002)和(111); FOX-12在水溶液条件下的主要晶面为(110)和(011), 在水/甲醇溶液条件下的主要晶面为(200)和(011), 预测的晶体形貌与实验结果相吻合. 对水分子和FOX-12的(110)面间的径向分布函数进行了计算, 分析了水分子和晶面间的分子间作用力.

关键词: N-脒基脲二硝酰胺盐, 晶体形貌, 分子动力学模拟, 修正附着能模型

Abstract:

The crystal morphologies of N-guanylurea-dinitramide(FOX-12) under solvent condition were investigated by molecular dynamics simulation with canonical(NVT) ensemble. The FOX-12 surface-solvent molecule adsorption model was constructed to simulate dynamical equilibrium configuration. By calculating the binding energies of solvent and crystal surfaces, the attachment energies in vacuum were modified and the crystal shapes in different solutions were obtained. The FOX-12 crystals were cultivated in H₂O and H₂O/MeOH by natural cooling and characterized by scanning electron microscopy. The results show that the morphologically dominant faces of FOX-12 in vacuum are (110), (200), (201), (011), (002) and (111); the (110) and (011) faces are found to be the morphologically important growth faces in H₂O; the (200) and (011) faces are found to be the morphologically important growth faces in H₂O/MeOH; the predicted crystal morphologies of FOX-12 were in agreement with the experimental results. Furthermore, the radial distribution function(RDF) analyses between H₂O molecules and (110) face of FOX-12 were performed to explore the solvent-crystal interactions.

Key words: N-guanylurea-dinitramide(FOX-12), Crystal morphology, Molecular dynamics simulation, Modified attachment energy model

TrendMD:

刘宁, 周诚, 舒远杰, 王伯周, 王文亮. N-脒基脲二硝酰胺盐晶体形貌的分子动力学研究. 高等学校化学学报, 2017, 38(12): 2231.

LIU Ning, ZHOU Cheng, SHU Yuanjie, WANG Bozhou, WANG Wenliang. Molecular Dynamics Simulations on Crystal Morphology of N-Guanylurea-dinitramide^†. Chem. J. Chinese Universities, 2017, 38(12): 2231.

图/表 11

Table 1 Comparison of the experimental and optimized lattice parameters of FOX-12

Model	a/nm	b/nm	c/nm	α/(°)	β/(°)	γ/(°)	ρ/(g·cm^-3)
Experimental^[4]	1.367	0.933	0.614	90.00	90.00	90.00	1.775
DREIDING	1.400	0.919	0.615	90.00	90.00	90.00	1.755
Relative error(%)	2.41	-1.50	0.01	0	0	0	-1.13

Fig.1 Unit cell structure of FOX-12

Table 2 Crystal habit parameters of FOX-12 crystal in vacuum predicted by the AE model*

(hkl)	Multiplicity	d_hkl/nm	E_att(total)/ (kJ·mol^-1)	E_att(vdW)/ (kJ·mol^-1)	E_att(H-bond)/ (kJ·mol^-1)	D	R_hkl	Total facet area(%)
(110)	4	0.771	-196.11	-78.44	-117.67	46.85	1.22	33.95
(200)	2	0.683	-161.32	-100.46	-60.86	38.54	1.00	18.27
(201)	2	0.457	-189.20	-128.46	-60.74	45.20	1.17	25.40
(011)	2	0.513	-221.85	-121.14	-100.71	53.00	1.38	14.70
(002)	1	0.307	-205.82	-205.53	-0.29	49.17	1.28	6.42
(111)	4	0.480	-237.76	-119.84	-117.92	56.80	1.47	1.26

Fig.2 Crystal morphology(A) and crystal graph(B) of FOX-12 in vacuum predicted by the AE model

Table 3 Accessible solvent surface area(Aacc) and total crystal face area(Abox) of FOX-12 surfaces calculated by the Connolly surface model

Species	(hkl)
Species	(110)	(200)	(201)	(011)	(002)	(111)
A_acc/nm²	0.5591	0.1485	0	0.2939	0	0
A_box/nm²	11.1434	5.1552	10.0328	11.2639	7.6519	9.1605

Fig.3 Configurations of FOX-12 surface-H2O interfaces from the MD equilibrium (A) (110); (B) (200); (C) (011).

Fig.4 Configurations of FOX-12 surface-H2O/MeOH interfaces from the MD equilibrium (A) (110); (B) (200); (C) (011).

Table 4 Interaction energies, modified attachment energies and relative growth rates of FOX-12 crystal habit faces in solvents

Solvent	(hkl)	E_tot/ (kJ·mol^-1)	E_surf/ (kJ·mol^-1)	E_solv/ (kJ·mol^-1)	E_int/ (kJ·mol^-1)	E_s/ (kJ·mol^-1)	$E' att$ / (kJ·mol^-1)	$R'* hkl$
H₂O	(110)	-31114.1	-29487.9	1862.1	-3488.3	-175.01	-21.10	1.00
	(200)	-28123.8	-26577.8	1630.5	-3176.5	-91.50	-69.82	3.31
	(011)	-31355.9	-29334.1	2183.8	-4205.6	-109.75	-112.10	5.31
H₂O/MeOH	(110)	-27888.6	-29487.9	5890.0	-4290.6	-215.28	19.17
	(200)	-24927.5	-26577.8	5657.9	-4007.7	-115.45	-45.88	1.00
	(011)	-28079.2	-29334.1	6057.7	-4802.8	-125.32	-96.53	2.10

Table 4 Interaction energies, modified attachment energies and relative growth rates of FOX-12 crystal habit faces in solvents

Solvent	(hkl)	E_tot/ (kJ·mol^-1)	E_surf/ (kJ·mol^-1)	E_solv/ (kJ·mol^-1)	E_int/ (kJ·mol^-1)	E_s/ (kJ·mol^-1)	$E' att$ / (kJ·mol^-1)	$R'* hkl$
H₂O	(110)	-31114.1	-29487.9	1862.1	-3488.3	-175.01	-21.10	1.00
	(200)	-28123.8	-26577.8	1630.5	-3176.5	-91.50	-69.82	3.31
	(011)	-31355.9	-29334.1	2183.8	-4205.6	-109.75	-112.10	5.31
H₂O/MeOH	(110)	-27888.6	-29487.9	5890.0	-4290.6	-215.28	19.17
	(200)	-24927.5	-26577.8	5657.9	-4007.7	-115.45	-45.88	1.00
	(011)	-28079.2	-29334.1	6057.7	-4802.8	-125.32	-96.53	2.10

Fig.5 Predicted crystal morphology(A) and SEM image(B) of FOX-12 from H2O

Fig.6 Predicted crystal morphology(A) and SEM image(B) of FOX-12 from H2O/MeOH

Fig.7 RDF analysis of H2O molecules and FOX-12 crystal for the (110) face (A) HFOX-12…OH2O; (B) HH2O…O FOX-12; (C) HH2O…NFOX-12.

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