The Surface Energy Of Ceramic And The Melting Of Nanostructured Drug

Many important physical and chemical processes occur at the surface and interface of materials, it is undoubtedly that researching the surface and interface microstructures and properties is crucial to control the physical and chemical processes and change the surface properties. With the development of ultrahigh vacuum technique and several complex surface microstructure analysis techniques, the scientific researchers have the ability to investigate the geometry, composition and chemical state of several atoms layers. Surface science, as a new subject, mixes the physics and chemistry, but also has its own characteristics, is becoming an important domain in recent research work. The study range is from massive and supermassive IC, thin films, to daily life, such as clothes, according to surface treatment to improve the antipollution and oil-proof abilities. Surface is boundary between the solid material and surrounding gas or vacuum, and interface energy γis a basic parameter to investigate the surface and interface, thus people do lots of theoretical and experimental work. In the aspect of theoretical research, since the presence of computer, computation abilities develop with astonishing speed, and improve the development of related scientific calculations. In 50 years of 20C, people introduced computer to material calculation and design, and then it became a new subject. Recently, with the development of modern scientific theory and the rapid progress of compute ability, material calculation and design become the most active branches in the material science. The main research methods are focused on Mont Carlo method, first-principle method, and molecular dynamic method et al. First-principle method, free of any adjustable parameter, is the most important method, which gets the electrical structure by solving the Schr?dinger equation. According to the first principle calculations, we can predict the compositions, structures and properties, especially the job that cannot be achieved by experiments. Ceramic material as one kind of three supporting industries is a potential material now and in the future. With the widely application, the relationship between the surface and material properties is more and more important, as their unique properties are closely related with its surface states, and then research, control and change surface properties will have great influences to the ceramic applications. Surface energy, as one of the basic qualities to understand the surface properties, is very hard to determine due to the limitation of experimental conditions, especially for the compounds. Therefore, a theoretical study of the surface energy is meaningful. According to the above conditions, in this thesis, based on the bond broken rule and density functional theory (DFT), we established the theoretical and computer simulation models for surface energy, and applied to the ceramic materials with the NaCl-structure, the results have been validated by the available data. Comparing with several simulation results, the results from LDA (local density approximation) method used in the paper are in agreement with the values from bond broken rule better, especially to stable exist ceramics including transition metal carbides, the transition metal nitrides, and the alkaline metal oxides. Although two models are very simple, it can give qualitative predictions for γvalues of compounds, provide the new method for researching the surface structures and properties. On the other hand, there is another world between the macroscopic one and the microscopic one, the mesoscopic world of the nanosystem where many special phenomena occur. Nanomaterials are the powder, block, thin film, multilayer film and fibre with the size between 1-100nm, which has become the hotspot in the study fieldfor material due to their special structure and performance. Now nanotechnology has become one of the three technology changing the survival and development for people apposed with information and biology. At the same time, nanotechnology is basic theoretical and technological foundation for the information and biological ones. Size is an important parameter for nanomaterials. Nanomaterials present different characters in acoustics, optics, thermodynamics and electromagnetics compared with the bulk ones. As the basic character, the melting temperature is related to the mechanical, physical and chemical performance. When it come to the study of drug, the bioavailability of the drugs depends on its solubility and dissolution rate, which can be amended by improving the drug absorption or permeability of the gut wall. Then the drugs are nanostructured are thus a unique way for amending absorption and bioavailability of poorly soluble drugs. It is known that the melting temperature of substances is an important parameter to determine diffusion rate of molecules, solubility and absorption amount of the molecules. Thus, once the size dependent melting temperatures of drugs are determined, the absorption behaviors, solubility and bioavailability of nanostuctured drugs are quantitatively determined, which will supervise the time dependent blood concentration of the nanostructured drugs and thus the therapy of patients. Base on the consideration mentioned above, a simple model without any adjustable parameter of size-dependent melting temperatures of nanostructured drug is built in this paper, which is applied to nanostructured griseofulvin (C17H17ClO6) and nifedipine (C17H18N2O6). It is found that when the size of the drugs drops to several...