In crystal structure, "rc/ra = 1" refers to the ratio of the radius of the central atom (rc) to the radius of the surrounding atoms (ra). This ratio is used to determine the packing efficiency of a crystal lattice.
The value of "<.23" in crystal structure indicates that the atoms in the lattice are arranged in a hexagonal close-packed (HCP) structure. This means that each atom is surrounded by six nearest neighbors, forming a close-packed layer.
In crystal structure, ">1" signifies that the unit cell of the crystal lattice contains more than one atom. This is common in many crystalline materials, where the unit cell may contain multiple atoms arranged in a specific pattern.
The value of "rc/ra" plays a crucial role in determining the density and strength of a crystal lattice. A higher value indicates a more tightly packed structure, which can result in greater strength and hardness of the material. A lower value may result in a less dense and weaker structure.
There are several factors that can influence the <.23 value in crystal structure, such as the size and shape of the atoms, the temperature and pressure conditions during crystal formation, and the presence of impurities or defects in the lattice. These factors can affect the arrangement and packing of atoms in the crystal structure, resulting in different values for <.23.