Impact of Advances in Computing and Communications Technologies on Chemical Science and Technology Report of a Workshop (1999) / Chapter Skim
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Session 1 Panel Disussion
Session 1 Panel Disussion
Pages 35-43
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From page 35... ...
But what I was particularly thinking about was not so much reimplementing the existing methodology we have, which I think has a number of disadvantages, some that I discussed and some that were, I think, clear by example in what John presented, but going back to, say, the Schrodinger equation and looking at other strategies for developing approximate solutions of it quite different from what we have now. So I would like to see an effort across the board on that, starting from looking again at the mathematics and looking at different methods for constructing approximate solutions all the way through.
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From page 36... ...
Thom Dunning, Pacific Northwest National Laboratory: I think just in general, to make very concrete the kind of suggestion Peter is making, that it has become painfully clear over the past decade how slowly basis-set expansions converge. Yes, we can approach the full solution of the Schrodinger equation with the basis-set technology that we have, but it is a very painful process and it gives rise to some of this very horrible scaling that Peter is talking about.
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From page 37... ...
If we put effort into understanding how to do higher derivatives of the energy efficiently (because we already know that evaluating the derivatives of the energy, at least up through fourth order, is something we can do a lot more efficiently than evaluating lots of individual energies) if say, we need derivatives through 25th order to characterize an entire potential energy surface and if we could figure out how to calculate the 25th derivative of the energy in an efficient way then we could do basically one calculation to characterize the whole thing.
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From page 38... ...
Peter Taylor: I would also like to address a general point that you raised there. There is a story, I believe told about Wigner, who said that rather than have a very accurate solution to the Schrodinger equation for behavior of electrons in a particular metal, which would necessarily be a very complicated thing, he would sooner have a vivid picture of what the electrons were doing in the metal.
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From page 39... ...
I think for the last 10 years we have been expanding the market for quantum chemistry in general and making it feasible to actually do computational inorganic and organic chemistry in a reasonably useful and reliable way. The market driving the development of methods for extremely large scale solutions, I think, is going to be somewhat smaller.
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From page 40... ...
If you want to look at chemistry at 298 or 500 degrees, you are after nuclear motion. If you want to treat the water dimer correctly you have to put quantum nuclear motion in, and I think that as we start to look at what we can do with the large architectures, we will actually start thinking about how we treat the nuclear motion problem, how we treat coupled routers, how we treat weakly bound systems.
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From page 41... ...
But the field is aware of this, and if we really wanted to have hard, small uncertainties, whether it is going the route of calculating upper and lower bounds or whatever, we would have to work very much harder in the calculation of the total energy itself than we are currently set up to do. Richard Kayser, National Institute of Standards and Technology: I wanted to point out that we have an effort under way to put together what we call a computational chemistry benchmark database.
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From page 42... ...
,lean Futrell, Pacific Northwest National Laboratory: I am not sure whether this is a showstopper or not, but I would like to inquire about the accuracy of present methods for defining transition states and their energetic properties, frequencies, and so on, and what one can expect from this leap forward in technology. John Pople: One difficulty is that my suggestion that we test theories by comparing with results known experimentally to great accuracy does not really hold for transition structures.
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From page 43... ...
Thom Dunning: While there have not been many calculations, there have been some that would certainly indicate that the techniques that we currently have available to us can achieve very high accuracy. It does turn out that calculations of transition states are significantly more challenging than calculations of stable species.
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