Ab Initio Quantum Chmistry Thermochemistry and Kinetics：量子化学从头热化学和动力学

1、“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.new approaches for teaching the chemical principles of engineeringphil westmorelanduniversity of massachusetts a“new approaches for teaching the chemical princip

2、les of engineering.” new england section conf., march 17-18, 2006.what are the chemical principles of engineering?principles that underlie the useful properties of atoms, molecules, macromolecules, continuum ensembles, materialsis it chemistry? is it physics? is it biology?biochemistry? physical che

3、mistry? chemical physics? physical organic chemistry? biophysical chemistry?quantum mechanics? statistical mechanics?semiconductor physics? organic semiconductors?i dont care! these are all “molecular sciences”.student need to master these principles - and can.molecular modeling and computer visuali

4、zation helps greatly!“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.che is the engineering profession that focuses on applying chemistry.phase and reaction equilibria bond and interaction energies ideal-gas thermochemistry thermoche

5、mistry and equations of state for real gases, liquids, solids, mixtures adsorption and solvationreaction kinetics rate constants, products metabolic pathwaystransport properties interaction energies, dipole , kthermal, dabanalytical information spectroscopy: frequencies, uv / vis /ir absorptivity gc

6、 elution times mass spectrometric ionization potentials and cross-sections, fragmentation patterns nmr shiftsprotein folding and misfolding, docking, adme, drug discoverymechanical properties of hard and soft condensed matterelectronic & optical properties“new approaches for teaching the chemica

7、l principles of engineering.” new england section conf., march 17-18, 2006.yes, che is the engineering profession that focuses on applying chemistry. but mechanical engineers use many properties that are molecular in origin. basic thermochemistry: fh, cp, s p-v-t relations strength of materials so d

8、o civil and environmental engineers chemical and biological treatment air, water, soil properties effects of environment on materials and likewise electrical and computer engineers band gap as collective homo-lumo differences.“new approaches for teaching the chemical principles of engineering.” new

9、england section conf., march 17-18, 2006.we all need to understand the chemical principles of engineering because we all need properties. maybe accurate, precisely known numbers. necessary for accurate design, costing, safety analysis. cost and time for calculation may be secondary. maybe “just” acc

10、urate trends and estimates. often more valuable. correlate with data to get high-accuracy predictions. use to identify relationships between structure and properties. enormous value for product and process development, operations, and troubleshooting. great data are best, but we must understand enou

11、gh theory to predicting unmeasured properties.“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.1. most property predictions are by correlations, wholly empirical or theory-based. arrhenius kinetics ideal gas law ideal gas mixtures (p=

12、xip= pi): ideal solutions activity coefficientsken jolls, /jolls/gibbspics/pvtn.jpg“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.2. property correlations require a grasp of underlying principles.“new approache

13、s for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.3. molecular visualization helps develop this grasp.compare the descriptions:(c33n3h43)fecl2,a liganded di(methyl imide xylenyl) aniline .nnnfeh3ch3cclcli-pri-pri-pri-pr“new approaches for teaching t

14、he chemical principles of engineering.” new england section conf., march 17-18, 2006.see functionality with the 3-d structure.“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.a key tool for describing molecular biology“new approaches

15、for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.such as enzymatic docking.5. for getting and using quantitative correlations properly, use the appropriate theory.lengthtime1 m100 m0.1 m10 nm1 nm1 ps10 ns1 hrcontinuum mechanicsstatistical mechanicsqu

16、antum mechanics(after maroudas, 2002)electronic structure theory molecular simulationswavefunction methodsdensity-functional theorysemi-empirical mo theoryab initio:basis setsmolecular dynamics,molecular mechanicsmonte carlo simulations(computational quantum chemistry)quantum md,car-parrinellopotent

17、ial energyfunctionsmolecular and material structurestatisticalmechanicsthermochemistry, kinetics, transport, materials properties, vle, solutions“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.6. we can use these computational tools

18、to help us teach about theory and applications.the educational principle: easy visualization and successful predictions motivate students to study useful underlying theories.“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.example: sk

19、etch ethylene; calculate optimized structure/frequencies/thermo; compare to data.calculations and graphics at hf/3-21g* with macspartan plus (wavefunction inc.).electrondensityhomo;lumo“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.

20、then theyll tackle “how” - the needed theory. maxwell-boltzmann and bose-einstein statistics. ideal-gas thermochemistry for cp and s, broken down into additive translation, rotation, vibration: compare with group additivity correlations. can develop transition-state theory quickly, logically.“new ap

21、proaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.energy efrom eh y posi t i on rx xx xx xw i t h energi es,w e can opt i m i zem ol ecul ar st ruct ureget bond lengths, bond angles, frequencies from analogies - or from quantum chemistry. eff

22、iciently explain the underlying quantum chemistry. easiest to think of a small, covalently bonded molecule like h2 or ch4 in vacuo. most simply, the goal of electronic structure calculations is energy. however, usually we want energy of an optimized structure and the energys variation with structure

23、.“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.for quantum mechanics, a hamiltonian operator is used for translational + kinetic energy. obtain a hamiltonian function for a wave using the hamiltonian operator:to obtain:where is the

24、 “wavefunction,” an eigenfunction of the equation born recognized that 2 is the probability density function“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.h-atom eigenfunctions y correspond to hydrogenic atomic orbitals.“new approac

25、hes for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.construct each mo yi by lcao. lennard-jones (1929) proposed treating molecular orbitals as linear combinations of atomic orbitals (lcao): linear combination of p orbital on one atom with p orbital

26、on another gives p bond: linear combination of s orbital on one atom with s or p orbital on another gives s bond:“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.simulate the real functionality with gaussians. start with a function th

27、at describes hydrogenic orbitals well.rtrue sto3 gaussianfunctions slater functions are “best”; e.g., gaussian functions are better; e.g., no s cusp at r=0 however, all analytical integrals linear combinations of gaussians; e.g., sto-3g 3 gaussian “primitives” to simulate a sto (“minimal basis set”)

28、“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.then explain hartree-fock, density functional theory, compound methods, and then.improved electron correlation pssssppssss“new approaches for teaching the chemical principles of enginee

29、ring.” new england section conf., march 17-18, 2006.7. use them to solve some small, real problems that reinforce the point. heat of combustion for dimethyloxirane safety. rate constant for simple reaction like c2h4+oh. heat of solvation for small molecules in various solvents. fit lennard-jones parameters for simple potential.“new approaches for teaching the chemical principles of engineering.” new england section conf., march 17-18, 2006.safety / reactor engineering example:“new approaches for teaching the chemical principles of engineering.” new england section conf., march