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1、Quantum Chemistry and Group theory,Dr. Ce Hao Room 228, Department of Chemistry Phone: 4708901 Cell phone: 13504966754 E-mail: URL: http:/ Introduction,Thermodynamics,Quantum mechanics,statistical mechanics,Thermodynamic method Quantum mechanic method Statistical mechanic method,0.1 Quantum chemist
2、ry,the branch of Physical chemistry the application of quantum mechanics to chemical problems, emerged as a new branch of chemistry.,0.2 The structure of science,Law a summary of experience,Hypothesis a tentative explanation that accounts for a set of facts and can be tested by further investigation
3、.,Theory a system of assumptions, accepted principles, and rules of procedure devised to analyze, predict, or explain the nature or behavior of phenomenon.,Model a simplified version of the system that focuses on the essentials of the problem.,0.2.1 Wave-function methods Pople,0.3 Density methods Ko
4、hn density functional theory,Chemistry is not only test tubes and chemicals. In quantum chemistry, quantum mechanics is used to compute the properties of molecules and their interaction to study molecules and chemical processes.,0.4 applications of Quantum chemistry,The three-dimensional structure o
5、f molecules can be accurately determined using quantum-chemical methods. One application of this is the development of new catalysts to generate very specific products such as drugs and plastics.,Applications in organic chemistry,Applications in biochemistry,By selecting a limited number of atoms (2
6、0-60) from the active site of an enzyme, bonding and reaction mechanisms can be studied with quantum-chemcial methods. The surrounding protein is described with simpler methods. The model below shows a possible mechanism of how myoglobin in muscles protects itself agains carbon monoxide poisoning. U
7、sing hydrogen bonding to one of the amino acids in the protein, oxygen can overcome the competition from the dangerous carbon monoxide.,Bibliography,I.N. Levine, Quantum Chemistry. Prentice Hall, Englewood Cliffs, NJ, 4th edition, 1991(有中译本，宁世光译） 2. John W. Norbury, QUANTUM MECHANICS,http:/ 3. http:
8、/ ID: qchem Pass word:12345 4. Peter R. Taylor Group Theory and its Applications http:/ 5. 量子化学中文网 http:/ Physics 2000 www.colorado.eduphysics2000index803e.html 7.曹阳，量子化学引论 8.唐敖庆， 量子化学,Rayleigh,Planck (1900),1.1.2 The Photoelectric Effect,According to the classical wave theory of light, the intensit
9、y of the light determines the amplitude of the wave, and so a greater light intensity should cause the electrons on the metal to oscillate more violently and to be ejected with a greater kinetic energy. In contrast, the experiment showed that the kinetic energy of the ejected electrons depends on th
10、e frequency of the light. The light intensity affects only the number of ejected electrons and not their kinetic energies.,1.1.3 Quantization of Electronic Angular Momentum,Rutherford (1901) proposed that electrons orbit about the nucleus of an atom.,Bohr assumed stable electronic orbits with the el
11、ectronic angular momentum quantized as l=mr=nh/2 E=h,Geometrical optics,Huygens(1690) the wave theory,Newton(1680) the particle theory,Interference and Diffraction “ether”,Thomas Young(1803),The Theory of Photons,（i）Photons: the particlelike aspect of light；,（ii）Energy of a photon,h,（iii） Mass of a
12、photon, m = hc2,（iv） Momentum of a photon, P mc hc h,Wave-Particle Duality of light,Einstein(1905),1.2.1 The Wave Character of Particles,Eh P h Planck-Eistain- de Broglie relations,Davisson and Germer (1925) “lucky accident”,Thomson,1.3 The Uncertainty Principle,(1) x0，Px； Px0，x。 It is impossible to
13、 specify simultaneously the precise position and momentum of any particle.,(2) Classical mechanics trajectory Quantum mechanics probability,Heisenberg(1927)， x Pxh/ 4,1.5 Wavefunction,The Uncertainty Principle xPxh/ 4,The state description Thermodynamics: Bulk properties(p,V,T,) Classical mechanics:
14、,de Broglie Hypothesis 1. Matter could also behave as waves. 2. Matter would obey the same equation as light Eh P h 3. The states of matter can be described by wavefunction. The 1-dimensional free particle:,1.5.1 Interpretation of the wavefunction,What is this wavefunction? What does it mean?,Born(1
15、926) suggested that wavefunction was that the square at a given point in space was proportional to the probability of finding the particle at that point in space.,The square is called the probability density while we can call the wavefunction is probability amplitude.,A single electron xPxh/ 4,A swarm of electrons,Probability density,Probability,Statistical definition:,Calculation of probability,Properties of probability,Probability deals with measuring or determining the likelihood that an event will have a particular outcome.,P(A)=0
