Computational Chemistry

function, each composed of two Gaussians, and an outer 2s,2px,2pyand 2pz(2s^00 , 2 px^00 ,2py^00 ,2pz^00 ) function, each compos ...

finer-tuning of the electron distribution and a lower energy, than would be possible with unsplit basis functions. A still more ...

(Table5.3) as the next bigger widely-used basis, the 6–31G (below) and is much less demanding of computer power, the 3–21G()basi ...

have a 1sorbital represented by an inner 1s^0 and an outer 1s^00 basis function, making two basis functions. Carbon has a 1sfunc ...

are found in molecules with heteroatoms, in anions, and in electronically excited molecules. To simulate well the behaviour of s ...

functions (6–31þG, 6–31þþG, 6–31þG and 6–31þþG) might be consid- eredfairlylarge. A large basis set might have a doubly-split or ...

2 s^002 p^00 2p^002 p^00 2 s^0002 p^000 2p^0002 p^000 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 3 d 4 f 4 f 4 f 4 ...

(Section 5.5.2.2b) use as part of their procedure single-point HF (rather than post- HF) level calculations with very large basi ...

(ECP) or a pseudopotential. With a set of valence orbital basis functions optimized for use with it, it simulates the effect on ...

5.3.3.8 Which Basis Set Should I Use? Scores, perhaps hundreds of basis sets have been developed, and new ones appear yearly, if ...

advanced post-Hartree–Fock methods suggest it is a true minimum on the potential energy surface, but its disconcerting tendency ...

structure is a minimum and the bridged nonclassical structure is a transition state, but with the 6–31G basis the bridged ion ha ...

can’t be in the same place at the same time. This is reflected in the Hartree–Fock formulation of the wavefunction as a determin ...

HF/3–21G(*)basis often gives good geometries (Section 5.3.3). Where necessary, the truncation problem can be minimized by using ...

A measure of the extent to which any particular ab initio calculation does not deal perfectly with electron correlation is theco ...

configuration interaction method like a complete active space SCF (CASSCF) calculation (Section 5.4.3). See too Section 8.2. Alt ...

experiment [ 80 ]). Althoughfrequenciesmust be calculated with the same method (HF, MP2, etc.) and basis set as were used for th ...

with and without the use of electron correlation methods, for processes involving homolytic cleavage, are discussed further inSe ...

We could writeEMP1¼EtotalHF ¼EMP0þEð^1 Þ, whereEMP0is the sum of one-elec- tron energies and internuclear repulsions and E(1) is ...

Eð^2 Þ¼ RR c 1 ð 1 Þc 1 ð 2 Þr^112  c 2 ð 1 Þc 2 ð 2 Þdv 1 dv 2 hi 2 2 ðe 1 #e 2 Þ ð 5 : 162 Þ Applying this formula “by hand” ...