Silicon--diamond cubic crystal structure

Silicon (Si) is a nonmetallic chemical element in the carbon family. Silicon makes up 27.7 percent of Earth's crust, the second most abundant element, surpassed only by oxygen. It is a semiconductor in group IVA of the periodic table with atomic number 14, an atomic weight of 28.086, and a 2.33 Mg/m3 density. It melts at 1410 C. The electronic configuration of the silicon atom is (Ne)(3s)2(3p)2, and the atomic radius is 0.132 nm.

Silicon has a diamond cubic crystal structure with a lattice parameter of 0.543 nm. The nearest neighbor distance is 0.235 nm. The diamond cubic crystal structure has an fcc lattice with a basis of two silicon atoms. Si is bonded to four equivalent Si atoms to form corner-sharing SiSi₄ tetrahedra. All Si-Si bond lengths are 2.36 Å.

As shown above, is a Face-centered diamond cubic crystal structure of silicon. The dark blue atoms are located at the edges of the unit cell, whereas the atoms depicted in light blue are positioned at the center of the outer faces. The silicon atoms illustrated in red are centered around three light blue atoms and one dark blue atom. The slab's normal vector (z-direction) is parallel to the [001]-direction of the silicon lattice, resulting in one degree of freedom; the orientation between the silicon's [100]-direction and the x-axis of the slab, which is quantified by the angle ϕ. The lattice constant of silicon (a SI ≈ 0.5 nm) is significantly smaller than the slab's thickness (d = 220 nm) such that the unpatterend silicon slab features a C 4 symmetry (b).

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