I mentioned “mindless chemistry” in the interview with Fritz Schaefer. This term, the title of the article by Schaefer and Schleyer,1 refers to locating minimum energy structures through a stochastic search driven solely by a computer algorithm. No chemical rationale or intuition is used; rather, the computer simply tries a slew of different possibilities and mindlessly marches through them.
The approach employed by Schaefer and Schleyer is to use the ‘kick” algorithm of Saunders.2 An arbitrary initial geometry is first selected (Saunders even suggests the case where all atoms are located at the same point!) and then a kick is applied to each atom, with random direction and displacement, to create a new geometry. An optimization is then performed with some quantum mechanical method, to produce a new structure. The kick is then applied to this new structure (or to the initial one again) to generate another geometry to start up another optimization. By doing many different “kicks” with different kick size, one can span a large swath of configuration space.
In their first “mindless chemistry” paper, Schafer and Schleyer identified some new structures of BCONS, C6Be and C6Be2-.1 In their next application,3 they explored the novel molecule periodane, which has the molecular formula LiBeBCNOF, named to reflect its make-up of one atom of every element (save neon) on the first full row of the periodic table. Krüger4 located the planar structure 1 (see Figure 1). But Schaefer and Schleyer, employing the “kick” algorithm located 27 structures that are lower in energy than 1, Their lowest energy structure 2 is 122 kcal mol-1 lower than 1. They advocate for this stochastic search to gain broad understanding of the nature of the potential energy surface and then refining the search using “human logic”.
1 |
 2 |
Figure 1. Optimized structures of periodane 1 and 2.
(Note – I have only provided a sketch of 2 since the supporting information for the article has not yet been posted on the Wiley web site. I will update this post with the actual structure when it becomes available.)
References
(1) Bera, P. P.; Sattelmeyer, K. W.; Saunders, M.; Schaefer, H. F.; Schleyer, P. v. R., "Mindless Chemistry," J. Phys. Chem. A, 2006, 110, 4287-4290, DOI: 10.1021/jp057107z.
(2) Saunders, M., "Stochastic Search for Isomers on a Quantum Mechanical Surface," J. Comput. Chem.. 2004, 25, 621-626, DOI: 10.1002/jcc.10407
(3) Bera, P. P.; Schleyer, P. v. R.; Schaefer, H. F., III, "Periodane: A Wealth of Structural Possibilities Revealed by the Kick Procedure," Int. J. Quantum Chem. 2007, 107, 2220-2223, DOI: 10.1002/qua.21322
(4) Krüger, T., "Periodane – An Unexpectedly Stable Molecule of Unique Composition," Int. J. Quantum Chem. 2006, 106, 1865-1869, DOI: 10.1002/qua.20948
Computational Organic Chemistry » Modification to the Kick algorithm (mindless chemistry) responded on 14 Aug 2008 at 10:41 am #
[…] Addicoat and Mehta1 have made a modification of the “Kick” algorithm. Recall, that the Kick method (discussed in this previous blog post) takes a collection of atom coordinates and applies a random kick to each atom. This creates a new initial configuration and a geometry optimization is performed starting form this configuration. If hundreds of such configurations are chosen, one hopes to locate most if not all reasonable structures. The new variation is to create fragments in which the atoms are held fixed. Then the kick is applied to the fragment as a whole. […]
Computational Organic Chemistry » More DFT benchmarks - sugars and “mindless” test sets responded on 19 May 2009 at 7:57 am #
[…] really not a “mindless” study (as the term is used by Schaefer and Schleyer3 and discussed in this post, where all searching is done in a totally automated way) but rather Grimme describes a procedure […]