Crystal Aggregation and Computer Modelling

生产药品、催化剂、精细化学品和其他工业重要材料的高效结晶工艺的设计取决于许多因素，包括产品本身的内部属性(如分子结构)、首选的晶体形状和大小以及内聚能，以及外部因素(如流体流动和阻力)。尽管所有这些因素都影响材料的聚集行为，但晶体在碰撞时的行为通常由单一的表达式来描述，该表达式没有考虑材料的特定属性，或者实际上将晶体的固有属性与拓扑考虑因素分开，例如碰撞粒子的相对几何形状。此外，既没有考虑碰撞粒子的形状或大小分布，也没有考虑作用在粒子上的力可能不仅仅是与撞击点垂直的事实，即使当两个粒子碰撞时剪切力可能非常重要。在这个项目中，我们打算对三种不同类型的材料的碰撞和聚集行为进行全面的研究，这些材料从纯无机材料(碳酸钙)到纯有机固体(己二酸)。我们将一方面使用计算化学方法和实验化学过程工程技术相结合，研究溶液中微晶的形状、碰撞颗粒的碰撞几何形状、碰撞颗粒之间的化学键以及碰撞后颗粒再次分离所需的剪切力和拉力。此外，我们将研究碰撞点处新物质的析出，导致粒子聚集，其中碰撞点可能确实是一维点、二维线或三维平面区域。一旦新材料在接合处生长，我们就可以计算出它的抗裂性。该项目的成果将是在原子水平上深入了解两个纳米晶体在溶液中碰撞时发生的化学和物理过程。此外，该项目的结果将使我们能够对一些有代表性的材料的聚集行为进行一般的数学描述，其中将包括固有的、与材料有关的性质和外部因素，包括溶剂效应(通过水阻力作用于颗粒的剪切力)和碰撞几何形状。通过结合这两种方法，我们的目标是开发一种定量的动力学描述，能够用于CFD来预测搅拌结晶器中的行为。

The design of an efficient crystallisation process for the production of pharmaceuticals, catalysts, fine chemicals and other materials of industrial importance is dependent on a number of factors, including internal properties of the product itself such as molecular structure, preferred crystal shape and size and cohesion energy, and external factors, such as fluid flow and drag. Although all of these factors affect the material's aggregation behaviour, the behaviour of the crystallites upon collision is usually described by a single expression, which does not take into account material-specific properties, or indeed separate intrinsic properties of the crystal from topological considerations, such as the relative geometries of the colliding particles. In addition, no consideration is given either to the colliding particles' shapes or size distribution, or the fact that the forces acting upon them may not just be normal to the point of impact, even though shear forces are likely to be very important when two particles collide. In this project, we propose to carry out a comprehensive study of the collision and aggregation behaviour of three different types of material, varying from a purely inorganic material (calcium carbonate) to a purely organic solid (adipic acid). We will use a combination of computational chemistry methods on the one hand and experimental chemical process engineering techniques on the other, to investigate the shapes of the crystallites in solution, the impact geometries of the colliding particles, the chemical bonding between the collided particles, as well as the shear and tensile forces required to separate the particles again after collision. In addition, we will investigate the precipitation of new material at the point of collision, leading to aggregation of the particles, where the collision point may indeed be a 1-D point, a 2-D line or a 3-D planar area. Once new material has grown at the join, we can calculate its resistance against fracture. The outcome of this project will be an in-depth understanding at the atomic level of the chemical and physical processes occurring upon collision of two nano-crystallites in solution. In addition, the results of the project will enable us to formulate general mathematical descriptions of the aggregation behaviour of a number of representative materials, which will include both intrinsic, material-dependent properties and external factors, including solvent effects (shear forces acting on the particles through water drag) and collision geometries. By combining these two approaches we aim to develop a quantitative kinetic description capable of being used with CFD to predict behaviour in stirred crystallisers.