TAILIEUCHUNG - Thermodynamics Interaction Studies Solids, Liquids and Gases 2011 Part 9

Tham khảo tài liệu 'thermodynamics interaction studies solids, liquids and gases 2011 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 390 Thermodynamics - Interaction Studies - Solids Liquids and Gases is direction dependent and is given by the expressions COSỚ a and sin 01 a in the X and y directions respectively figure 3 with a the distance to nearest neighbour function of the type of atomic packing and 0 the inclination of the overall crystal shape resulting from the total number of steps being created. The surface energy is given by the expression ESurf cosớ sinớ 2fl2 with sb the energy per bond. The broken bond model can be used to determine the shape of a small crystal from the minimization of the sum of surface energies y over all crystal faces a concept introduced in 1878 by J. w. Gibbs considering constant pressure volume temperature and molar mass . i at constant energy hence adding the constraint dE 0 . The dependence of y on orientation of the crystal s surface and its equilibrium shape are condensed into a Widffplot in 1901 George Wulff stated that the length of a vector normal to a crystal face is proportional to its surface energy in this orientation. This is known as the Gibbs-Wulff theorem which was initially given without proof and was proven in 1953 by Conyers Herring who at the same time provided a two steps method to determine the equilibrium shape of a crystal in a first step a polar plot of the surface energy as a function of orientation is made given as the so-called gamma plot denoted as y n with n the normal to the surface corresponding to a particular crystal face. The second step is Wulff construction in which the gamma plot determines graphically which crystal faces will be present Wulff construction of the equilibrium shape consists in drawing a plane through each point on the y-plot perpendicular to the line connecting that point to the origin. The inner envelope of all planes is geometrically similar to the equilibrium shape figure 4 . Fig. 4. Wulff s construction to calculate the minimizing surface for a fixed volume Thermodynamics of Surface Growth with .

• Cơ khí - Chế tạo máy
• ơ khí chế tạo máy
• tài liệu cơ khí
• sổ tay cơ khí
• hướng dẫn cơ khí
• ôn thi cơ khí
• Kỹ Thuật
• Công Nghệ
• Cơ khí
• Chế tạo máy
• Chẩn đoán cụm bánh xe
• Moay ơ
• Lốp