英语翻译HuÈ ckel argues that the ®rst of these terms,where the (p)hstate of carbon [p…p† orbital in modern notation] issingly occupied,should be the energetically lowest-lyingterm for benzene; therefore,only this term is consi

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英语翻译HuÈ ckel argues that the ®rst of these terms,where the (p)hstate of carbon [p…p† orbital in modern notation] issingly occupied,should be the energetically lowest-lyingterm for benzene; therefore,only this term is consi
英语翻译
HuÈ ckel argues that the ®rst of these terms,where the (p)h
state of carbon [p…p† orbital in modern notation] is
singly occupied,should be the energetically lowest-lying
term for benzene; therefore,only this term is considered
in the mathematical treatments of the electronic struc-
ture.In the ®nal section of part 2 HuÈ ckel says that he is
going to use two di€erent mathematical treatments for
the benzene problem.He calls them ``®rst method'' and
``second method'',which are now known as Valence
bond (VB) and MO methods,respectively.HuÈ ckel cites
papers by Heitler and London [1],Heisenberg [16],
Slater [17],and Bloch [18] as fundamental for the ®rst
(VB) method and says that he is going to use Bloch's
version for his work.For the second (MO) method he
cites another paper by Bloch [19] and the famous
publication of Hartree [20],but not Fock [21].HuÈ ckel
writes that Hartree's approximation neglects exchange
interactions,but he notes that this can be accounted for
later in the calculations.Before coming to the two
central mathematical parts of the paper,HuÈ ckel notes
that ``...it will be seen that the second method is better
suited for the real behaviour than the ®rst method.''
In the third part of the paper HuÈ ckel derives energy
expressions for the di€erent electronic terms of benzene
using method 1.The wavefunction is given as a Slater
determinant,and the solution of the SchroÈ dinger equation
is expressed in analogy to the Heitler±London paper [1] as
where DW is the interaction energy between the n p
electrons which is determined by the coulomb integrals
J0 and the exchange integrals J.3 The equations for
determining DW and a are then given as
‰DW ÿ nJ0 ‡ …n ÿ t† JŠal ‡ J
X
at ˆ 0 …3†
HuÈ ckel uses symmetry and group theoretical arguments
to ®nally derive (in chapter 5) the following energy
expressions for n electrons in n-cyclic CH compounds
given by method 1:
Chapter 4 describes the energy expressions for p
electrons in cyclic conjugated systems using the familiar
integrals a,for the energy of an unperturbed electron,
and b,for the interaction between electrons at neigh-
bouring atoms.HuÈ ckel notes that b > 0 if the wave-
function is nodeless,while b < 0 when the wavefunction
has a node (HuÈ ckel de®nes a and b in such a way that
positive values are stabilizing and negative values
destabilizing).
The important part of this chapter concerns the
wavefunction.HuÈ ckel cites Bloch [19] and notes that,for
cyclic groups,each wavefunction,v,may be expressed as...