Announcements:• Assignment #4 due on Monday• Friday – no official class, but I will be in 111 Boucke (or here?) if you need help with HyperChem or have other questions• try to read leach Optimization handout we will discuss on MondayToday:• just going over people’s questions (from Ass. #3 +)(1) Potential energy surface (PES) needs more clarification. The textbook is very vague on this matter.(2) The section from Cramer that we did not discuss was the geometry optimization. If that was covered in more detail, it might help understanding and applying it.(3) Possibly going over a broad description of force fields that are available and their properties and application characteristics would create a better understanding of force fields as a whole, and their differences between each other.(4) Cross terms not always very clear.________________________________________________I think we could have discussed the zero point energy and its contributions a little more. I still do not really understand where this energy comes from. I also would appreciate some comparison of these force field energies with those from experimental chemistry. It would be easier for me to understand all these graphs and such if there were some of the same data generated by experiment, not by computer.________________________________________________- multipole expansion (reading unclear)- 1,4 interactions how many 1,4 interactions there could be seemed fuzzy- PES for more than 3-atom molecule- “calculating force fields”________________________________________________- more explanation of electrostatics and how they are applied to molecular mechanics- what are some benefits of various force fields, what distinguishes class I from class II and how should select the best FF for a given problem________________________________________________- multipole moments hard to visualize- hydrogen bonding potentials________________________________________________- further clarification of the parameters of the torsionalpotential would be great; for example on the problem from #17 of Worksheet 2, how do we know what parameters must be zero and not?- more examples of how to sketch PES for simple molecules- a little more clarification on out of plane terms, and basically why do the terms become more unrealistically stiffwe haven’t talked much about [computational] cost in this; what do we need to know?Topics for ClarificationFig. adapted from: Steinfeld et al., Chemical Kinetics & Dynamics (Prentice-Hall, 1999))(NelRErPortion of the PES of C5H12Figure from Leach’s text (Ch. 5)Example: Simple Water Models for Liquid Simulations from: Jorgensen et al., J. Chem. Phys. 79, 926 (1983).Table 4.3 & Figs. from Leech2.27 2.18 2.352.17μ/ D(σ/A, ε/kB/K)(3.17, 78) (3.17, 78) (2.96, 157) (3.15, 78)(3.15, 77) (3.10, 38)μgas= 1.85 Dμliq~ 2.6 Dfigure from Cramer’s textH3CCHOH2CCH2Otable from Jensen’s
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