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Лекция 4 Химическая связь. Строение молекул . PowerPoint PPT Presentation


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Лекция 4 Химическая связь. Строение молекул. Ronald James Gillespie 1 9 2 4 -. Walter Kohn 19 23 -. Двухатомные молекулы с гетероатомами. Н F. Последовательное s – p смешение (гибридизация ). sp. sp 3. sp 2. s - sp. Molecular Orbital Diagram (HF).

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Лекция 4 Химическая связь. Строение молекул .

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4

4

. .

Ronald James Gillespie

1924 -

Walter Kohn

1923 -


4

F


4

s p ()

sp

sp3

sp2

s - sp


Molecular orbital diagram hf

Molecular Orbital Diagram (HF)

HF makes a linear zig-zag structure with 2 hydrogen bonds


4

sp2


4

s p ()


4

II

LUMO

HOMO


4

s p

s(p-p), p(p-p), p(p-p)


4

s p

s(sp-sp2), p(p-p),


4

s -

p -

s -

p -


4


4

- -

.

?

?


4

,


4


4

Occupied (top) and selected virtual (bottom) HF molecular orbitals of water


H 2 o molecule and liquid water

H2O molecule and liquid water

Hatree-Fock level with Sadlej basis set using the DALTON program on 32 nodes of the T3E computers at the NSC in Linkping

Guo et al., Phys. Rev. Lett. 89, 137402 (2002)

Finding: an electron sharing takes place between water molecules. Such a sharing mainly involves the so-called 3a1 orbital, which is a mixing of oxygen 2p and hydrogen 2s atomic orbitals.


4

Plasma Orbital Expansion Theory

Normal Water Byproduct

Torch

Browns Gas

Picture Found at:

http://www.wikibooks.com/Vidos/BrownsGas.html

Target substance

= Electrons

H = Hydrogen

O = Oxygen

--- = Bonding

Electrons scatter in all directions

producing a high heat plasma


4

, 1 4,6 107 / 58 .

() !!


Rydberg clusters

Rydberg Clusters

Possible Rydberg cluster found in Browns Gas


4

(CO2)

OO

?

C

?


4

THE MOLECULAR ORBITAL CONTOUR DIAGRAM FOR CARBON DIXOIDE


4

(CO2)

OO


4

2

Orbital 11 - E = 2.35 eV


4

(CO2)


4

CO2

s-p c


4

2 ?

,


4

HOMO -LUMO -(CO2)


4

-


4

,


4

Interaction of CO2 with Transition Metal Centers

Reactive positions of CO2 molecule & electronic properties of a transition metal centre required for complexation

Orbital overlapping & electrostatic interaction

of coordination modes of CO2

Structural types of metalCO2 complexes


4


4

2 ,

SiO2

sp2 sp2


4

sp3


4

sp2 SiO2


The crystal structure of quartz

The Crystal Structure of Quartz

  • Quartz is crystalline silica (SiO2) at temperatures below 870C

Figure 2 The -quartz crystal lattice structure

Figure 1 The Natural Form of Quartz


The piezoelectric effect

The Piezoelectric Effect

Crystal material with forces applied

in direction of arrows..

Crystal

- - - - -

Force

+ + + + +

Current Meter

deflects in +

direction

Due to properties of symmetry,

charges are net + on one side &

net - on the opposite side: crystal gets

thinner and longer


4

What Is the Piezoelectric Effect?


4

(.. ). .

  • 1880. ( , , 1859-1906,

  • . : , ,

  • , ,

  • .


4

  • x1, ) , x1.

    , .

  • .


4

  • :

  • .

  • , , , 0.


Piezoelectricity

Piezoelectricity

  • displacement of electrical charge due to the deflection of the lattice in a naturally piezoelectric quartz crystal

  • The larger circles represent silicon atoms, while the smaller ones represent oxygen.

  • Quartz crystals is one of the most stable piezoelectric materials.


4

A common feature of high-performance piezoelectric materials is the existence of a triple point in the compositiontemperature phase diagram.


4

The unit cell of crystal silicon dioxide

-

+

+

-

-

+


4

A pushing force:

(aka: compression)

A pulling force:

(aka: tension)

+

-

-

-

+

+

+

+

-

-

-

-

+

+

+

-


4

Piezoelectric

materials


4

Molecular Orbitals of Ammonia


4

TSC Orbitals of H3


4

d(N-H) = 0,102 nm

a = 107,8

d(P-H) = 0,144 nm

a = 93,3

d(As-H) = 0,144 nm

a = 91,8


4

d(P-F) = 0,157 nm

a = 97,8

d(P-Cl) = 0,204 nm

a = 100,1

d(P-Br) = 0,218 nm

a = 101,5

d(P-I) = 0,243 nm

a = 102


4


4


Molecular orbital diagram ch 4

Molecular Orbital Diagram (CH4)


4

  • Propagation Step 1:

    • One of the chlorine atoms abstracts a hydrogen atom from a methane molecule:


4

4


4

Dyson orbital NH4 aniona

-

NH4


4

Shape of the t2 LUMO derived from an MP2/aug-cc-pVTZ calculation f Li(NH3)4.The red and purple colors indicate opposite phases of the orbital


4

II


4

II


4

II


4

II


Inherent structure and excess electron dynamics of water cluster anions h 2 o n

Inherent structure and excess electron dynamics of water cluster anions, (H2O)n

John M. Herbert

Department of Chemistry

University of California, Berkeley


Aa binding motif

AA binding motif

see Nathan Hammer (FD09):


Dodecahedral h 2 o 20 isomers

(H2O)20 VDEs

Dodecahedral (H2O)20 isomers

See Joseph Bopp (FD11)

Expt

A. Khan, JCP 118,

1684 (2003)

B3LYP/6-311++G**//

B3LYP/6-31G*

X3LYP/6-31++G* geometries


Dodecahedral h 2 o 20 isomers1

(H2O)20 VDEs

Expt

Dodecahedral (H2O)20 isomers

X3LYP/6-31++G* geometries


Dodecahedral h 2 o 20 isomers2

(H2O)20 VDEs

Expt

Dodecahedral (H2O)20 isomers

X3LYP/6-31++G* geometries


H 2 o 24 isomers with m 0 0

cavity states

414 fused

cubic

4668 tetra-

dechedrons

41464 edge-

sharing prisms

51262 tetra-

decehedrons

(H2O)24 isomers with m0 0

Expt


Questions

Questions


4


4

1.

2.

3. ,

4. , ,

5.

6. (LUMO), (HOMO), SOMO?

7. Dyson orbital ?

8..


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