Computational Chemistry

000

000

000

0

B

@

1

C

A¼

100

010

001

0

B

@

1

C

A

000

000

000

0

B

@

1

C

A

100

010

001

0

B

@

1

C

A

(1)

• 
  

+

• 
  

0 +

• 
  

0 +

0

–1

1

–2

2

0

Three p atomic orbitals.

Chapter 4, Harder Questions, Answers

Q4

How might thei,j-type interactions in the simple H€uckel–Fock matrix be made to
assume values other than just#1 and 0?
Such changes in the Fock matrix have been made in an attempt to handle systems
with orbital contributions from atoms other than carbon. Consider the two species

and

A B

C

C

C

..-

H

H

H H

C

C ..

H

H

H H

H

1 N

2

(^31)
2
3
H
The matrix for the all-carbonpsystem A is that shown in the answer to
question 3. The matrix for the hetero (nitrogen) system B is qualitatively similar,
but its 2,3 and 3,3 interactions should be different from those of A:
Answers 613