Rules

1. Points are given similar to football, i.e. a "like" gives +3 points, "neutral" +1 points, no answer at all ("Vot en blanc","None Of The Above") 0 points, "hate" -1 points. A ranking of the functionals will be made by taking into account these points.


2. In case there are two or more functionals with the same number of points, the ordering will be decided by the following criteria: (i) most number of "like"s, (ii) least number of "hate"s, (iii) results from previous years (for future editions), (iv) year of publication of the functional (the younger, the better), (v) decision by organizers.


3. There will be a Primera Divisió with the 20 most popular functionals. At the end of each year, the 5 least popular of the Primera Divisió will relegate to the Segona Divisió.
   Each year, only the 20 most popular functionals of the Segona Divisió will be kept. The five most popular ones of the Segona will be promoted to the Primera, while the 15 next will form the Segona for the next year together with the 5 relegated from the Primera.
   The other functionals will not take part in the poll for the year after (unless suggested again). There is a maximum of 10 additional suggestions for each year, which are added chronologically (after being suggested by mail to M. Swart).
   PS. for the 2011 edition of next year, the 20 most popular functionals of 2010 will form the Primera, the other 10 the Segona Divisió. There will be 20 places left in the Segona Divisió of 2011 for additional suggestions.


4. A new PACO functional will be constructed each year, by taking a weighted linear combination of the 20 functionals in the Primera Divisió. For those functionals that do not have an energy expression (e.g. SAOP, LB94), a weight of zero will be used for the construction of PACO20xx.
   The weight of each functional is given by its number of points, divided by the total number of points of the 20 functionals in the Primera Divisió (using a value of 0 for those without an energy expression, see above). The sum of the weights is therefore one.


5. The PACO20xx functionals will (starting with the 2015 edition) *no longer* be applied to a small number of typical applications:
   • the AE6 set for atomization energies
   • the BH6 set for barrier heights
   • the π-π stacking energy of anti-parallel cytosine dimer
   • spin-state splitting of FeFHOH and Ni(EDT)₂^2-
   • excitation energies (singlet, triplet) of CO
   • the hydrogen-bonding energies of four dimers (ammonia, water, formic acid, formamide)
   • For all of these CCSD(T) or experimental reference data are available.
   Instead, for those interested, one can use the data from Grimme's GMTKN30 database with the PACO201x coefficients.


6. Each year, a new popularity poll will be held between June 1 and October 1, (and be announced on this page, on the CCL list, etc.) and a short news item about it will be published. In this news item, the ranking and results of the applications will be reported.


7. The organization of the DFT-poll reserves the right to disqualify density functionals in case of clear proof of cheating. This disqualification remains effective for the year following the year in which the cheating has been observed.


8. For a few years, from 2015 to 2018, the DFT Popularity Poll included a third question
   where participants could give their preferences for the density functionals for a total of 11 properties (1. Reaction barriers; 2. Normal mode analysis (vibrational frequencies, thermodynamics); 3. Chiroptical properties; 4. Hydrogen bonds; 5. Excitation energies; 6. Main group elements; 7. Transition metals; 8. Relativistic elements; 9. NMR shieldings, NMR couplings; 10. Geometries; 11. Spin-state splittings). These results should be of value for starting researchers in the field, to give a balanced overview of the application of these density functionals to the study of these 11 properties. The results will be highlighted in the news-item of each year, with all detailed statistics for each functional being made available completely on www.marcelswart.eu/dft-poll. To make these results more useful, a total of five levels of preferences can be given: Love it (++), Like it (+), Neutral (0), Dislike it (-), Hate it (--). These levels will be assigned the following points respectively: +3, +1, 0, -1, -3, to make rankings for each of the properties as well. No distinction will be made between Primera and Segona Divisió for this third question.