In crystallography, atomic packing factor (APF) or packing fraction is the fraction of volume in a crystal structure that is occupied by atoms. It is dimensionless and always less than unity. For practical purposes, the APF of a crystal structure is determined by assuming that atoms are rigid spheres. The radius of the spheres is taken to be the maximal value such that the atoms do not overlap. For one-component crystals (those that contain only one type of atom), the APF is represented mathematically by
where Natoms is the number of atoms in the unit cell, Vatom is the volume of an atom, and Vunit cell is the volume occupied by the unit cell. It can be proven mathematically that for one-component structures, the most dense arrangement of atoms has an APF of about 0.74. In reality, this number can be higher due to specific intermolecular factors. For multiple-component structures, the APF can exceed 0.74.
Read more about Atomic Packing Factor: APF of Common Structures
Famous quotes containing the words atomic, packing and/or factor:
“When you see something that is technically sweet, you go ahead and do it and you argue about what to do about it only after you have had your technical success. That is the way it was with the atomic bomb.”
—J. Robert Oppenheimer (1904–1967)
“The good husband finds method as efficient in the packing of fire-wood in a shed, or in the harvesting of fruits in the cellar, as in Peninsular campaigns or the files of the Department of State.”
—Ralph Waldo Emerson (1803–1882)
“In his very rejection of art Walt Whitman is an artist. He tried to produce a certain effect by certain means and he succeeded.... He stands apart, and the chief value of his work is in its prophecy, not in its performance. He has begun a prelude to larger themes. He is the herald to a new era. As a man he is the precursor of a fresh type. He is a factor in the heroic and spiritual evolution of the human being. If Poetry has passed him by, Philosophy will take note of him.”
—Oscar Wilde (1854–1900)