Transcript Introduction to theoretical chemistry 2 semesters

special topic in physics AP4174
an introduction to electronic
orbital theory
The specific goals of the course are:
•to analyze the nature and behaviour of electronic
orbitals
•to show how we can use the characteristics of
orbitals in order to:
– make a material more stable in energy
– change the binding between atoms to modify the
structural, physical and chemical properties of
materials to achieve desired results
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The following questions will be
treated:
• What can we learn about the stability and properties of a
material by analyzing its electronic orbitals? Such knowledge
will allow more powerful prediction. What was known before?
• Why is it necessary to consider quantum mechanics? Why
does classical mechanics fail?
• What is an electronic orbital?
• What are the nature and behaviour of molecular orbitals? How
can we build them from simple “intuition” and symmetry? How
can we build molecular orbitals with elementary methods
(such as the Huckel approach)?
• Which information do the electronic orbitals provide?
• How can we manipulate the electronic orbitals? A brief
introduction to the versatile perturbation theory.
• How can we achieve greater precision when needed? A brief
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introduction to more accurate calculations.
Representation and modeling of Molecules
This is an introductory course to present both
the traditional representations of the molecules and the concepts behind
an initiation to quantum mechanics and to orbital theory
No mathematical pre-requisite is necessary. The first part is for beginners in
chemistry or physicist not familiar with chemical language. The second part of the
course will first justify why QM approach is necessary at the atomic level, next briefly
introduce operators and wave functions and finally shows that simple approaches
are affordable an only use well known comprehensive tools. With the progression of
the course, the mathematics will progressively disappear in favor of pictorial and
qualitative descriptions.
Manipulating orbitals, a qualitative view of orbitals.
This is an introductive course on Molecular Orbital theory and modeling. The
emphasis is made on concepts such as symmetry preservation and not in
calculations. Introduction to calculations methods will focus on the input-outputs and
on their validity domain (How to choose them? How to use them? What are the
limitations?). The MO theory is applied to prediction and analysis of structures and
reactivity. The courses of the two semesters are independent even though it is better
to take them successively.
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AP4273-AP8273
an introduction to electronic orbital theory
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AP4273-AP8273
an introduction to electronic orbital
theory,
Counting electrons
Lewis structure
SO32-
Molecular orbital
CCl4
Atomic orbitals
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Different ways of counting and representing electrons
Planar representation
Lewis structure
SO32-
* *
* **
Spatial Representation
VSEPR
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How to guess a geometry?
Search for total energy minimum
Improve stability of orbitals
Orbital of H2O 1b2 favors linearity and 1a1 bending
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Butadiene
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LCAO
MOs are made of AOs
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2 different phases
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Butadiene
-.3717
What can we learn ?
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An electronic description
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(measure the bond strengths
And delocalisation)
Information on structure
(avoid connecting the “ends”) 0.6015
Information on reactivity
(react from both ends…
More …
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The “conservation of the HOMO”
hn
D
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HF
The orbital approximation consists to
treat the electrons as independent.
Electrons are not independent.
HF
preserves
the
orbital
“independency” by taking as orbital
that consistent with the average
distribution of the others.
This method is iterative (self
consistent) and satisfies the Pauli
principle.
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Electronic correlation
Correlation requires to take into
account the relative positions of
the electron that are quite never
the average place.
• VB method and
polyelectronic functions
• IC (beyond HF)
• DFT
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Skip! Sleep if you want!
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For clarity, simple structures will be used to
illustrate the concepts and methods of this
course. An introduction to calculations for
larger structures (including periodic
crystals) and a presentation of codes are
planned to conclude this course.
There are no pre-requisites to enroll in this
course. An active participation by the
students is expected.
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Christian MINOT
G6620
[email protected]
Flexibility (lecture and tutorial),
please let me know how to
adapt.
Code demonstrations
Controls of knowledge.
Questions?
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