Concluding Remarks Bound Triplet Pairs

As we noted in the introduction, spectroscopic evidence is available for small no-pair dimers and trimers [4a,b,c, 5a,b,c,d, 6a,b, 7] and therefore the elucidation of NPFM bonding is not a mere academic exercise. An additional potential interest in this kind of clusters is their relationship to Bose-Einstein condensates, in which the quantum states of all atoms are identical, and to Fermi gases of fermionic isotopes of alkali metals, (e.g., K with atomic mass 40) in magnetic fields [6, 19]. 

Finally, having maximum magneticity, no-pair clusters are also interesting for their potential applications in nanochemistry. 

A more complete mini-periodic table of NPFM bonding wiU have to include the heavy alkali metals (K, Cs, Rb, Fr), and the group III metalloids, such as B, Al, and so on. In view of the importance of the ionic stractures, the heteroatomic clusters may be even more strongly bonded. Thus, even though the principles of NPFM bonding are clear, still some future work thus lies ahead. 

For all these reasons, and for the mere fact that NPFM is a novel bonding form, it is essential to draw the attention of the community to these clusters. 

The DFT calculations presented here were obtained with B3P86, in combination with cc-pVDZ for Li clusters, and St-RECP for coinage metals, hence, UB3P86/St-RECP. Specifically, UB3P86/St-RECP was shown [2e,f to have a very small basis set superposition error (BSSE), and was compatible with the results of the extended augmented double zeta atomic natural orbital (ANO) basis set of Roos et al. [28] Other DFT methods were tried, and the results were similar to UB3P86 [2f.  

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