Metallic bond: band electron theory In 1927, Walter Heitler and Fritz London, students of postdoctoral with Schrödinger, applied Linear Combination of Atomic Orbitals to metals. Let's apply the Linear Combination of Atomic Orbitals for Copper. We start doing the linear combination for two neighbor atoms, not to violate the Pauli exclusion principle (same energy and opposite spins). From the linear combination of the two atomic orbitals (A), we have two molecular orbitals (A2): a sigma-bonding and a sigma-antibonding. Before doing the linear combination of (A2) with a third atom, also neighbor, we must note that the presence of this atom changes the energy of (A2). The combination of (A2) with the third atom (A) forms a molecular orbital (A3). Repeating the Linear Combination of Atomic Orbitals for a large number of atoms (n), we get two bands of energy: a Valece Band and a Conduction Band Let's apply the Linear Combination of Atomic Orbitals for solid semiconductors and insulators. The energy gap between the Valence Band and Conduction Band determines the boundary between a semiconductor and an insulator (2.5 to 3.0 eV).

• published: 07 Nov 2013
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