Structure of metals | lattice types | body-centered cubic, face-centered, hexagonal | bcc, fcc, hcp скачать в хорошем качестве

Structure of metals | lattice types | body-centered cubic, face-centered, hexagonal | bcc, fcc, hcp

Metals have a regular lattice structure that significantly influences their physical properties. In this video, we explain the structure of different lattice types and their effects on material properties. First, we examine metallic bonding, which is responsible for holding atoms together. In this process, metal atoms release their outer electrons, resulting in positively charged metal ions surrounded by an electron gas. The lattice structure forms due to the interplay between attractive and repulsive forces acting between the metal ions and the electron gas. The atoms arrange themselves in a regular pattern to achieve a more energetically favorable state. This arrangement is called a crystal lattice. A characteristic parameter of this structure is the lattice constant, which refers to the distance between two adjacent atoms. It typically ranges from 250 to 500 picometers. The unit cell represents the smallest repeating unit of a crystal lattice. There are different lattice types, distinguished by atomic arrangement and packing density. One important structure is the body-centered cubic (bcc) lattice, where, in addition to atoms at the corners of the unit cell, an additional atom is located at the center of the cube. Typical metals with this structure include iron, chromium, and tungsten. They have a packing density of approximately 68% and a coordination number of 8, meaning each atom is in direct contact with 8 neighboring atoms. Another significant lattice structure is the hexagonal close-packed (hcp) lattice. Here, the atoms are arranged in a hexagonal pattern, allowing for particularly dense packing. Metals such as titanium, cobalt, zinc, and magnesium exhibit this lattice structure. The atoms are arranged in a stacking sequence in which each atomic layer is packed as tightly as possible. The packing density is 74%, and the coordination number is 12. A special form of the hexagonal lattice can be found in graphite. Unlike metals, whose lattices are held together by metallic bonds, graphite consists of carbon atoms arranged in hexagonal layers. These layers are only weakly bonded by van der Waals forces, allowing them to slide easily over one another. This property explains why graphite is commonly used as a lubricant or as the material for pencil leads. In addition to body-centered cubic and hexagonal lattice structures, there is also the face-centered cubic (fcc) lattice. In this structure, atoms are not only positioned at the corners of the unit cell but also at the center of each face of the cube. This structure also has a packing density of 74% and a coordination number of 12. Metals with this lattice structure include aluminum, copper, nickel, and lead. The deformability of a metal is directly related to its lattice structure. While metals with a face-centered cubic structure are particularly soft and easily deformable, metals with a hexagonal structure are relatively brittle and break more easily. Body-centered cubic metals fall in between, as they are deformable but not as much as face-centered cubic metals. 00:00 Structure of metals 00:28 Metallic bonding 00:58 Formation of lattice structures 02:17 Lattice constant 03:08 Unit cell 04:04 Body-centered cubic lattice (bcc) 05:47 Hexagonal closest packed lattice (hcp) 07:21 Hexagonal lattice structure of graphite (hex) 08:18 Face-centered cubic lattice (fcc) 09:58 formability of lattice structures