References
- (a) Minkin VI, Minyaev RM, Zakharov II, Avdeev VI (1978) Zh Org Khim 14:3. (b) Minkin
VI, Minyaev RM (1979) Zh Org Khim 15:225. (c) Minkin VI, Minyaev RM, Orlova GA (1984)
J Mol Struct (Theochem) 110:241 - (a) Minyaev RM, Minkin VI, Zefirov NS, Zhdanov YuA (1979) Zh Org Khim 15:2009. (b)
Minyaev RM, Minkin VI, Zefirov NS, Natanzon VI, Kurbatov SV (1982) Zh Org Khim 18:3 - (a) Lewars E (2000) J Mol Struct (Theochem) 507:165. (b) Lewars E (1998) J Mol Struct
(Theochem) 423:173 - Lewars E (2008) Modeling marvels. Computational anticipation of novel molecules. Springer,
The Netherlands
Chapter 7, Harder Questions, Answers
Q1
It is sometimes said that electron density is physically more real than a wavefunc-
tion. Do you agree? Is something that is more easily grasped intuitively necessarily
more real?
First I will summarize a debate, at the level of polemic in some cases, about the
relative merits of the wavefunction and the electron density function, then close
with a few personal observations. The principal participants in the argument were,
on the wavefunction side, Gernot Frenking, and on the electron density side,
Richard Bader, and Ronald Gillespie and Paul Popelier. The recent history of the
controversy starts in 2003 with a review by Frenking [1] of a book on chemical
bonding by Gillespie and Popelier [2]. In his long review, Frenking commended the
book to readers, but criticized its emphasis on electron density and its virtual
ignoring of the wavefunction: “Like Bader, the authors reject the wavefunction as
a basis for the explanation of molecular geometries because it is not a physical
observable...It is hard for human beings to accept that the fundamental principles of
elementary quantities of science are not accessible to their sensory perception.”
Gillespie and Popelier responded to these criticisms, but conceded that “The
question of whether the wave function or the electron density is the more funda-
mental is perhaps open to dispute” but defended electron density as “much more
useful for understanding chemical bonding and molecular geometry” [3]. Frenking
defended his criticisms and reiterated that “The wavefunctionC, which is funda-
mental to our science, is a mathematical object which is not accessible to human
senses.” He made the important point that “the important class of pericyclic
reactions could only be explained with MO theoretical arguments using the sym-
metry ofC.”, a symmetry not present in the electron density. He chides the two
authors for using ease of understanding as the reason for choosing electron density
overC, and closes by “encouraging interested readers” to study the book and his
review and make up their own minds [4].
636 Answers