I just returned from the Southwest Theoretical Chemistry Conference held at Texas A&M University. My thanks again to Steven Wheeler for the invitation to speak at the meeting and for putting together a very fine program and conference.

Among the many interesting talks was one by Sebastian Kozuch who reported on an interesting double hybrid methodology.^{1,2} Working with Jan Martin, they defined a procedure that Kozuch referred to as “putting Stefan Grimme into a blender”. They extend the double hybrid concept first suggested by Grimme that adds on an MP2-like correction functional. Kozuch and Martin substitute a spin-component scaled MP2 (SCS-MP2) model for the original MP2 correction. SCS-MP2 was also proposed by Grimme. Lastly, they add on a dispersion correction, an idea championed by Grimme too. The exchange-correlation term is defined as

*E _{XC}* =

*c*+ (1 –

_{X}E_{X}^{DFT}*c*)

_{x}*E*+

_{x}^{HF}*c*+

_{C}E_{C}^{DFT}*c*+

_{O}E_{O}^{MP2}*c*+

_{S}E_{S}^{MP2}*s*

_{6}E_{D}where *c _{X}* is the coefficient for the amount of DFT exchange,

*c*the amount of DFT correlation,

_{C}*c*and

_{C}*c*the amount of opposite- and same-spin MP2, and

_{S}*s*the amount of dispersion. They name this procedure

_{6}**DSD-DFT**for

**D**ispersion corrected,

**S**pin-component scaled

**D**ouble hybrid

**DFT**.

In their second paper on this subject, they propose the use of the PBEP86 functional for the DFT components.^{2} Benchmarking against a variety of standard databases, including kinetic data, thermodynamic data, along with inorganic and weakly interacting systems, this method delivers the lowest mean error among a small set of functionals. Kozuch reported at the conference on a number of other combinations and should have a publication soon suggesting an even better method. Importantly, these DSD-DFT computations can be run with most major quantum codes including *Orca*, *Molpro*, *Q-Chem* and *Gaussian* (with a series of IOP specifications).

While double hybrid methods don’t have quite the performance capabilities of regular DFT, density fitting procedures offer the possibility of a significant reduction in computational time. These DSD-DFT methods are certainly worthy of fuller explorations.

### References

(1) Kozuch, S.; Gruzman, D.; Martin, J. M. L. "DSD-BLYP: A General Purpose Double Hybrid Density Functional Including Spin Component Scaling and Dispersion Correction," *J. Phys. Chem. C*, **2010**, *114*, 20801-20808,

DOI: 10.1021/jp1070852

(2) Kozuch, S.; Martin, J. M. L. "DSD-PBEP86: in search of the best double-hybrid DFT with spin-component scaled MP2 and dispersion corrections," *Phys. Chem. Chem. Phys.* **2011**, *13*, 20104-20107, DOI: 10.1039/C1CP22592H