Lec8 (1) - 10.675 LECTURE 8 RICK RAJTER 1. Today Basis Sets...

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10.675 LECTURE 8 RICK RAJTER 1. Today ”Basis Sets” Linear combination of atomic orbitals (LCAO) contraction split valence polarization functions diffuse functions basis set super position error (BSSE) 2. Basis Sets 2 types: local and non-local. Localized basis sets (what gaussian uses) Non-localized basis sets (plane waves) frequencies are much less sensitive to basis sets than the energy Zero point energy is a destabilizer. 3 NkT Rotational 2 3 NkT Vibrational 2 LCAO choose a ”basis set” for each atom and sum them for the ”molecular” basis set. ζr Example, Slater orbitals. f ( x, y, z ) e αr = ( (2 ζ ) n +1 / 2 n 1 e ao [(2 n )!] 1 / 2 ) r - Numerical - Gaussians s : ce αr 2 p : c xe αr 2 ... (3 total) x,y,z d : c x 2 e αr 2 ... (6 total) xx, yy, zz, xy, yz, xz Examples of ”Basis Sets” ”Minimal basis set” - fewest # of functions needed to treat all electrons. H-1 Li-2 C-3.
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This note was uploaded on 11/27/2011 for the course CHEMICAL E 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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Lec8 (1) - 10.675 LECTURE 8 RICK RAJTER 1. Today Basis Sets...

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