有机膦系抑制方解石阶梯面生长的分子动力学研究

有机膦系化合物是工业冷却水系统中常用阻垢剂,对有机膦酸阻垢剂的阻垢性能及机理进行研究,能为新型阻垢剂开发应用提供合理的理论依据。根据周期性键链（PBC）理论模型,运用分子动力学方法（MD）,模拟了工业冷却水循环过程中5种有机膦阻垢剂与方解石4种阶梯面的相互作用机理。结果表明,有机膦酸分子与方解石（104）4个阶梯面的结合能均为负值,相互作用为放热过程,阻垢剂分子对方解石（104）阶梯面的生长具有良好的抑制作用。通过计算结合能,得出阻垢剂分子的吸附能力由强到弱依次为HDTMP、EDTMP、ATMP、NDP、AMP;同时观察到有机膦酸分子主要吸附在晶面的活性生长点,即阶梯面的终端拐角位置与阶梯拐点位置,占据了晶面上结晶的活性位置,抑制了晶面的进一步生长。根据有机膦酸与阶梯面结合能数据,得到4种终端阶梯面的吸附能力由强到弱依次为CO₃-CO₃、CO₃-Ca、Ca-CO₃、Ca-Ca,即稳定性越强则吸附能力越弱。     

4种吡嗪类缓蚀剂及其在Cu(111)面吸附行为的密度泛函理论研究

为了探究吡嗪类缓蚀剂对铜的缓蚀机理,对比研究4种缓蚀剂的吸附性能。采用基于密度泛函理论（DFT）的量子化学方法,研究了4种吡嗪类缓蚀剂分子的反应活性及其在Cu（111）面的吸附行为,结果表明：4种缓蚀剂分子的前线轨道均分布在吡嗪环上,且吡嗪环上的N原子为分子的反应活性中心;4种吡嗪类缓蚀剂分子均能与Cu原子发生化学吸附形成共价键,且吸附强度排序为2-氨基吡嗪（AP）> 2-氨基-5-溴吡嗪（ABP）> 2-甲基吡嗪（MP）> 吡嗪（PY）;另外,缓蚀剂分子也可以通过静电相互作用与金属表面发生物理吸附。     

基于第一性原理的铁基表面腐蚀性研究

采用密度泛函理论(DFT)第一性原理,分析了焦炉煤气中的主要腐蚀性物质H2S、HCN在铁基表面的吸附性质以及腐蚀分子与基体发生作用后的成键情况,并计算了吸附能和分波态密度(PDOS)。结果表明,H2S分子与Fe的表面相互作用要强于HCN分子,说明焦炉煤气中的H2S对铁基表面的腐蚀性较大。     

金红石型TiO_2(011)晶面的表面化学研究进展

综述了采用高分辨扫描隧道显微镜(STM)等表面技术和密度泛函理论(DFT)计算等手段对TiO2(011)晶面的表面化学研究的进展,重点介绍了(011)面的表面结构组成、乙酸分子的吸附及诱导重构现象、水分子的吸附及产生的吸附氢原子的迁移和反应等方面的研究成果,揭示了TiO2表面结构与其化学性质的相互关系,为在原子尺度上理解TiO2催化材料的作用机理创造条件。     

6种燕尾形苝二酰亚胺类双子表面活性剂对碱性锌电极缓蚀机理理论研究

为了研究燕尾型苝二酰亚胺类双子表面活性剂对碱性锌电极缓蚀机理,利用密度泛函理论（DFT）和分子动力学模拟（MD）方法,探讨了两类共6种燕尾型苝二酰亚胺类双子表面活性剂的吸附行为。DFT计算结果表明,前线分子轨道分布主要位于分子核心的苝二酰亚胺骨架上,且苝二酰亚胺骨架上的N原子为分子的反应活性中心。分子动力学模拟表明,6种燕尾型苝二酰亚胺类双子表面活性剂均能与水溶液中的金属锌表面发生相互作用,N₂、P₂在两类双子表面活性剂中均表现出有较高的吸附能和较大的扩散系数,吸附能分别为-11315.868 kcal/mol、-10785.698 kcal/mol,扩散系数分别为2.5、1.32;研究结果同时表明,N₂和P₂形成的双子表面活剂膜层对腐蚀粒子OH^-的阻止效果较好,能够在金属锌表面起到很好的缓蚀效果。     

尿素(520)晶面可控结晶的分子动力学模拟

由于尿素结晶呈白色针状,晶貌单一,且传统结晶工艺不可控,严重影响药物的一致性评价结果。采用分子动力学模拟方法,从分子水平上研究不同种类的添加剂对尿素晶体生长的调控作用,揭示添加剂对药物晶体生长的调控机制。结果表明：① 六种添加剂(海藻糖、蔗糖、葡萄糖、山梨醇、赖氨酸、精氨酸)在101.325 kPa、290 K下相较于无添加剂时都能不同程度地抑制(520)晶面的生长;② 添加剂对尿素晶面(520)的吸附能越负,其抑制晶面生长效果越好,其中海藻糖抑制(520)晶面生长效果最好;③ 添加剂分子携带基团的种类与数目决定与晶层的相互作用的强弱,特别是海藻糖、蔗糖双糖类分子含有8个羟基,与晶层上的尿素分子氢键相互作用强,与溶液层中的溶质形成竞争性吸附,能更好抑制(520)晶面生长。     

尿素(520)晶面可控结晶的分子动力学模拟

由于尿素结晶呈白色针状,晶貌单一,且传统结晶工艺不可控,严重影响药物的一致性评价结果。采用分子动力学模拟方法,从分子水平上研究不同种类的添加剂对尿素晶体生长的调控作用,揭示添加剂对药物晶体生长的调控机制。结果表明:(1)六种添加剂(海藻糖、蔗糖、葡萄糖、山梨醇、赖氨酸、精氨酸)在101.325kPa、290 K下相较于无添加剂时都能不同程度地抑制(520)晶面的生长;(2)添加剂对尿素晶面(520)的吸附能越负,其抑制晶面生长效果越好,其中海藻糖抑制(520)晶面生长效果最好;(3)添加剂分子携带基团的种类与数目决定与晶层的相互作用的强弱,特别是海藻糖、蔗糖双糖类分子含有8个羟基,与晶层上的尿素分子氢键相互作用强,与溶液层中的溶质形成竞争性吸附,能更好抑制(520)晶面生长。     

一种新型小分子电镀铜整平剂的模拟研究

以2,2′-二硫代二吡啶（2-PDS）和铜分别作为研究对象和研究基体，并以量子化学计算、分子动态模拟为理论模拟方法，通过模拟2-PDS与铜表面的相互作用和相互反应，得出2-PDS分子可以通过自身丰富的活性位点和较强的成键能力紧密地吸附在铜表面上以阻碍铜离子的沉积，这也表明了2-PDS分子是一种潜在的整平剂。     

ε-CL-20在二元混合溶剂中晶体形貌的分子动力学模拟

利用分子动力学模拟的方法探究了乙酸乙酯与二溴甲烷组成的二元溶剂在298.15 K,1 atm下对ε-CL-20晶体形貌的影响。通过修正附着能模型(MAE)模型探究了溶剂-晶体相互作用,用分子动力学模拟预测了不同组成的乙酸乙酯/二溴甲烷混合溶剂中ε-CL-20的晶体形貌并与实验获得ε-CL-20的晶体形貌进行了对比。结果表明,实验获得的晶体形貌与模拟结果一致,且晶面粗糙度越大,溶剂-晶体相互作用越强。此外,还通过均方位移(MSD)分析了溶剂分子在不同晶面的扩散系数,探究了溶剂扩散速率对不同晶面的影响,并利用径向分布函数(RDF)分析了溶剂分子与晶体分子间相互作用的组成。     

C1-C7直链烷烃在MFI沸石内吸附行为的分子模拟

本文用巨正则系综蒙特卡罗（GCMC）及构型偏移蒙特卡罗（CBMC）的方法模拟了300K时C1—C7直链烷烃分子在MFI沸石分子筛中的吸附行为，并用目前常用的几种吸附理论对之进行拟和。包括单双点Langmuir吸附等温式、拟化学近似吸附等温式及Gibbs吸附等温式。双点Langmuir吸附等温式取得了最好的拟和效果。模拟及拟和结果说明了MFI沸石内通道吸附性能具有非均一性，也说明了吸附分子间相互作用对分子在沸石中的吸附行为的影响不能忽略，所以若要建立描述的客体分子在沸石内的吸附行为的较好模型，推导模型时必需考虑沸石的这种非均一性及吸附分子之间的相互作用。     

Morphology prediction for organic molecular crystals using various force fields in ADDICT

All-atom force fields are important for calculating interaction energies between growth units to predict crystal morphology. Our group at UCSB developed the ADDICT morphology design software to predict crystal morphology using mechanistic growth models driven by the generalized Amber force field (GAFF). In this study, the universal force field (UFF), the consistent force field (CFF), and the Coulomb-London-Pauli (CLP) force field are incorporated into ADDICT. We systematically test the lattice energies and crystal morphologies of olanzapine, adipic acid, rubrene, biphenyl, and naphthalene using all these force fields. The unit cells for these crystals are represented by the original CSD experimental structure, as well as optimized structures. Considering the high accuracy of CLP, its wide range of applications, and the fact that ADDICT can automatically specify the atomic charge and type required for this force field, we find that CLP is the best all-atom model to drive morphology calculations.     

不同组分比的HMX/DMI共晶炸药结构与性质的理论研究

利用分子动力学,研究了分子摩尔比对HMX/DMI共晶炸药几个重要晶面成键能的影响,对于不同分子的摩尔比的力学性质也进行了估算,借助M06-2x/6-311+G(2df,2p)方法对HMX/DMI复合物的溶剂效应也进行了研究。计算结果表明,(020)和(100)取代基模型具有最高的成键能和稳定性,1∶1和2∶1的化合物最稳定且具有最高的力学性能。分子间相互作用能和N–NO_2键离解能的变化对HMX/DMI共晶炸药的稳定性有较大影响。制备稳定的HMX/DMI共晶炸药应选用较低介电常数作溶剂。     

Molecular Insight into the Self-Assembly Process of Cellulose Iβ Microfibril

The self-assembly process of β-D-glucose oligomers on the surface of cellulose Iβ microfibril involves crystallization, and this process is analyzed herein, in terms of the length and flexibility of the oligomer chain, by means of molecular dynamics (MD) simulations. The characterization of this process involves the structural relaxation of the oligomer, the recognition of the cellulose I microfibril, and the formation of several hydrogen bonds (HBs). This process is monitored on the basis of the changes in non-bonded energies and the interaction with hydrophilic and hydrophobic crystal faces. The oligomer length is considered a parameter for capturing insight into the energy landscape and its stability in the bound form with the cellulose I microfibril. We notice that the oligomer–microfibril complexes are more stable by increasing the number of hydrogen bond interactions, which is consistent with a gain in electrostatic energy. Our studies highlight the interaction with hydrophilic crystal planes on the microfibril and the acceptor role of the flexible oligomers in HB formation. In addition, we study by MD simulation the interaction between a protofibril and the cellulose I microfibril in solution. In this case, the main interaction consists of the formation of hydrogen bonds between hydrophilic faces, and those HBs involve donor groups in the protofibril.     

活性助剂在超细滑石粉填充三元乙丙橡胶中的应用研究

研究了活性助剂三烯丙基异氰脲酸酯(TAIC)和N,N一间苯撑双马来酰亚胺(MPBM)以及硅烷偶联剂Si一69和钛酸酯偶联剂NDZ201对超细滑石粉填充三元乙丙橡胶重点硫化特性和力学性能的影响。结果表明,TAIC和MPBM具有较高的反应活性,在适当的用量下可以提高胶料的拉伸强度和撕裂强度;硅烷偶联剂Si一69和钛酸酯偶联剂NDZ201均可增进滑石粉与EPDM分子的结合,在适当的用量下可以改善胶料的力学性能,使得胶料的玻璃化转变温度升高,而Si一69可与EPDM分子形成化学键结合,所以其偶联效果比NDZ更为明显。     

偶联剂改性UHMWPE纤维表面性能的研究

选用硅烷偶联剂KH-550,KH-560和钛酸酯偶联剂NDZ-201作为表面改性剂,对超高相对分子质量聚乙烯(UHMWPE)冻胶纤维在萃取阶段进行表面处理,经干燥、超拉伸制得表面改性UHMWPE纤维。采用红外光谱仪、接触角测量仪测定了纤维的表面化学结构和表面润湿性能,采用单纤维树脂包埋-拔出法测定了纤维与树脂基体的界面剪切强度,比较了改性前后纤维的力学性能变化。结果表明:改性后纤维表面引入了极性基团,硅烷偶联剂KH-550对UHMWPE纤维的表面改性效果最好。采用质量分数为1%的硅烷偶联剂KH-550溶液处理后,纤维与环氧树脂间的界面剪切强度提高了87.8%,纤维的断裂强度和模量分别提高了6.9%和32.6%。     

3D QSAR pharmacophore modeling, in silico screening, and density functional theory (DFT) approaches for identification of human chymase inhibitors

Human chymase is a very important target for the treatment of cardiovascular diseases. Using a series of theoretical methods like pharmacophore modeling, database screening, molecular docking and Density Functional Theory (DFT) calculations, an investigation for identification of novel chymase inhibitors, and to specify the key factors crucial for the binding and interaction between chymase and inhibitors is performed. A highly correlating (r = 0.942) pharmacophore model (Hypo1) with two hydrogen bond acceptors, and three hydrophobic aromatic features is generated. After successfully validating "Hypo1", it is further applied in database screening. Hit compounds are subjected to various drug-like filtrations and molecular docking studies. Finally, three structurally diverse compounds with high GOLD fitness scores and interactions with key active site amino acids are identified as potent chymase hits. Moreover, DFT study is performed which confirms very clear trends between electronic properties and inhibitory activity (IC(50)) data thus successfully validating "Hypo1" by DFT method. Therefore, this research exertion can be helpful in the development of new potent hits for chymase. In addition, the combinational use of docking, orbital energies and molecular electrostatic potential analysis is also demonstrated as a good endeavor to gain an insight into the interaction between chymase and inhibitors.     

The Effect of Water on Matrix/Filler Adhesion in a Polyurethane Elastomer

The static “moduli”, failure stresses and dynamic moduli of both filled and unfilled polyurethanes were measured over a range of equilibrium water contents and these results are compared with those obtained from dry controls. Where barium sulphate was employed as the major filler component, it is shown that the presence of as little as ∼0.7% water results in a profound degradation of mechanical properties with the loss of most of the contribution attributable to the presence of fillers as a result of hydrolytic disruption of filler/matrix adhesion. A quantitative relationship between water content and mechanical properties is established and the mechanics of the water/polymer/filler interaction are considered. Less dramatic effects were observed when barium sulphate was replaced by iron oxide and these were apparently further reduced by the use of a silane coupling agent.     

膦酰基羧酸对碳酸钙的阻垢机理

通过透射电镜、扫描电镜和X射线衍射仪分析了投加膦酰基羧酸（POCA）对碳酸钙形貌及晶格参数2θ的影响，发现投加POCA改变了CaCO₃垢的结晶习惯并对方解石有一定的晶格扭曲作用，随着加药量的增加，方解石的比例减少，而文石和球霰石的比例增加，POCA对方解石（110）晶面的抑制作用强于（104）晶面;同时采用分子动力学(MD)方法，模拟计算了POCA与方解石的(110)、（104）晶面的相互作用， 结果表明：聚合物分子与晶面之间的结合能主要由Coulomb作用和van der Waals作用力提供。比较POCA在方解石两晶面上的结合能，发现E_bind(110)大于E_bind(104)，两者数值之比约为1.39，即POCA分子与(110)面的结合比(104)面更牢固，说明POCA对(110)面生长的抑制居于主导地位。两种研究方法得到的结论一致。     

DFT Studies of Selected Epoxies with Mesogenic Units–Impact of Molecular Structure on Electro-Optical Response

Theoretical studies of molecular structure and electric charge distribution were carried out for three epoxy compounds with different mesogenic cores. The compounds exhibit a nematic phase and form polymer networks that are potential bases for various composites. Results were compared to analogous materials with non-polar chains. A customized process involving geometry optimization of a series of conformations was employed to greatly increase likelihood of reaching global energy minimum for each molecule. All computations used Density Functional Theory (DFT) electron correlation model with the B3LYP hybrid functional. Molecular structure calculations yielded several parameters, including the magnitude and direction of the dipole moment, polarizability (α), first hyperpolarizability (β), and highest-occupied/lowest-unoccupied molecular orbital (HOMO-LUMO) energies. These parameters can help predict electronic properties of the nematic phase and the polymer network and assess their predisposition for application in electrooptical devices. In particular, the magnitude and direction of the dipole moment determine molecular alignment of liquid crystal phases in electric field, which enables controlling molecular order also in cured networks. Theoretical results were supplemented with observations of the nematics and their behavior in electric field. It was demonstrated for the studied compounds that a change in aliphatic chain polarity helps preserve and reinforce perpendicular alignment of molecules induced by electric field.