Why the crystal structure of NaCl is FCC and not BCC?

Why the crystal structure of NaCl is FCC and not BCC?

Hint: NaCl has a cubic unit cell. It is best thought of as an FCC array of anions with an inter penetrating FCC cation lattice. The cell looks the same whether you start with anions or cation on the corners. Each ion is 6 coordinate and has a local quadrilateral geometry.

How is NaCl FCC?

NaCl has a cubic unit cell. It is best thought of as a face-centered cubic array of anions with an interpenetrating fcc cation lattice (or vice-versa). The cell looks the same whether you start with anions or cations on the corners. Each ion is 6-coordinate and has a local octahedral geometry.

Why FCC crystal structure are usually more ductile than BCC metals?

This is because their symmetry provides closely packed planes in several directions. A face-centered cubic crystal structure will exhibit more ductility (deform more readily under load before breaking) than a body-centered cubic structure. The bcc lattice, although cubic, is not closely packed and forms strong metals.

Why are BCC stronger than FCC?

Yes the APF is important, the atomic packing factor, that is the reason FCC has more slip systems, because of the way the atoms are arranged in the crystal. Thus FCC metals deform easier than BCC metals and thus they are more ductile. BCC metals are infact stronger than FCC metals. HCP metals are the most brittle.

What type of crystal structure is the NaCl crystal?

cubic crystals
Rock salt also known as NaCl is an ionic compound. It occurs naturally as white cubic crystals. The structure of NaCl is formed by repeating the unit cell. It has an organized structure and has a 1:1 ratio of Na:Cl.

Is HCP stronger than BCC?

BCC metals are less ductile but stronger, eg iron, while HCP metals are usually brittle. Zinc is HCP and is difficult to bend without breaking, unlike copper.

Is BCC less ductile than FCC?

FCC metals tend to be more ductile than BCC metals because of their different slip systems. There are 12 total slip systems, 5 independent. If there are at least 5 independent slip systems, the metal is ductile! BCC crystals have 48 slip systems but still only 5 are independent.

What is the strongest crystal structure?

Rendering of a diamond. Currently, diamond is regarded to be one of the hardest and most scratch-resistant natural materials in the world. Most diamonds found in nature and often used in jewelry display a cubic crystal structure, a repeating pattern of 8 atoms forming a cube with carbon atoms at its vertices.

How does NaCl structure differ from a standard FCC stucture?

Easy answer: NaCl has two different ions (one at origin, the other at the center of unit cell), while the standard FCC is only one. Complete answer: both NaCl and a standard FCC structure belong to the space group Fm-3m. And Fm-3m has two distinguished Wyckoff positions with a multiplicity 8.

What’s the difference between BCC and fcc crystal structure?

For some space, in FCC materials, about 74% of the space is occupied by atoms, leaving 26% of the space empty. In BCC materials, 68% of the space is occupied by atoms, so 32% of the space is empty. FCC actually has the most efficient atomic arrangement possible (tied with HCP).

How to find the coordination number of sodium chloride ( NaCl )?

FCC is packing of an element. For, NaCl, it’S not simply Na or Cl its a combination of both; in NaCl, each Na+ is surrounded by 6 Cl- and vice versa. so, coordination number is 6. its structure can actually thought to be: Cl- ions in cubic closed packed arrangement with octahedral holes filled by Na+ ions.

What are interstitial sites in BCC and FCC?

Interstitial Sites in FCC and BCC FCC and BCC crystal structure also have different arrangements of interstitial sites. Interstitial sites are the places in the unit cell between atoms. You already know that unit cells of metals are not fully packed (74% for FCC and 68% for BCC), which means they have some empty space.