MP2.X: a generalized MP2.5 method that produces improved binding energies with smaller basis sets

• Published in: Physical chemistry chemical physics : PCCP 2011-12, Vol.13 (47), p.21121-21125
• Main Authors: Riley, Kevin E, ezá, Jan, Hobza, Pavel
• Format: Article
• Language: English
• Subjects: Binding energy; Chemistry; Errors; Exact sciences and technology; General and physical chemistry; Models, Chemical; Organic Chemicals - chemistry; Physical chemistry; Static Electricity; Thermodynamics
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c1cp22525a

In this article we present binding energy results for a scaled MP2.5 method along with several basis sets. The accuracy of the methods tested here is determined by comparison to reference data in the newly developed S66 data set of interaction energies. It is found that scaling of the MP2.5 correction term results in strongly improved binding energies for small basis sets, such as 6-31G* and 6-311++G**. The scaling parameter for larger basis sets, such as aug-cc-pVDZ and aug-cc-pVTZ, approaches a value of 0.50, which corresponds to the original (unparametrized) MP2.5 method. It is found that the MP2.X method yields S66 RMS errors of approximately 0.15 kcal mol −1 for all basis sets. In addition to generally providing more accurate binding energies than MP2.5, MP2.X generally produces a more well-balanced description of noncovalent interactions, yielding better binding energies for dispersion-bound and mixed dispersion-electrostatic complexes. Scaling of the MP2.5 correction term allows for the use of much smaller basis sets with almost identical accuracy.