Molecular complexes and molecular clusters represent a broad class of systems with interesting chemical and physical properties. Such systems can be naturally partitioned into fragments each representing a molecule or several molecules. Q-Chem contains a set of methods designed to use such partitioning either for physical or computational advantage. Some of these methods (e.g. the ALMO-EDA method and its most recent updates/extensions) were developed and implemented by Dr. Rustam Z. Khaliullin, Dr. Paul R. Horn, Dr. Yuezhi Mao, Dr. Jonathan Thirman, Dr. Daniel S. Levine, Dr. Qinghui Ge, and Matthias Loipersberger working with Prof. Martin Head-Gordon at the University of California–Berkeley. Other methods [e.g., the XSAPT family of methods and TDDFT(MI)] were developed by Drs. Leif Jacobson, Ka Un Lao, and Jie Liu working with Prof. John Herbert at Ohio State University.
The list of methods that use partitioning includes:
Initial guess at the MOs as a superposition of the converged MOs on the isolated fragments
J. Chem. Phys.
(2006), 124, pp. 204105.
Automated calculation of the BSSE with counterpoise correction method (full SCF and RS implementation).
The original version the ALMO-EDA method (energy decomposition analysis based on absolutely localized
molecular orbitals), including the associated charge transfer
J. Phys. Chem. A
(2007), 111, pp. 8753. , 596 J. Chem. Phys.
(2008), 128, pp. 184112. , 516 J. Chem. Phys.
(2013), 138, pp. 134119. and the analysis of intermolecular bonding in terms of complementary occupied-virtual pairs (COVPs). 596 J. Chem. Phys.
(2008), 128, pp. 184112. , 597 Chem. Eur. J
(2009), 15, pp. 851. , 516 J. Chem. Phys.
(2013), 138, pp. 134119.
The second-generation ALMO-EDA method,
Phys. Chem. Chem. Phys.
(2016), 18, pp. 23067. , 780 Annu. Rev. Phys. Chem.
(2021), 72, pp. 641. , 512 J. Chem. Phys.
(2015), 143, pp. 114111. , 514 J. Chem. Phys.
(2016), 144, pp. 114107. , 779 Phys. Chem. Chem. Phys.
(2020), 22, pp. 12867. including its extension to single-bond interactions 713 J. Chem. Theory Comput.
(2016), 12, pp. 4812. , 711 J. Phys. Chem. Lett.
(2017), 8, pp. 1967. , 712 Proc. Natl. Acad. Sci. USA
(2017), 114, pp. 12649. and the ALMO-EDA(solv) scheme 781 Chem. Sci.
(2021), 12, pp. 1398. for the inclusion of implicit solvents in EDA calculation.
Closed- and open-shell AO-XSAPT(KS)+D, a dispersion-corrected version of XSAPT in atomic orbital
basis that affords accurate intermolecular interaction
energies at very low cost.
J. Phys. Chem. Lett.
(2012), 3, pp. 3241. , 668 J. Chem. Phys.
(2013), 139, pp. 034107. , 670 J. Phys. Chem. A
(2015), 119, pp. 235.
A stable and physically-motivated energy decomposition approach, SAPT/cDFT,
in which cDFT is used to define the charge-transfer component of the interaction energy and
SAPT defines the electrostatic, polarization, Pauli repulsion, and van der Waals
J. Chem. Theory Comput.
(2016), 12, pp. 2569.
The electrostatically-embedded many-body
J. Chem. Theory Comput.
(2007), 3, pp. 46. , 1028 J. Chem. Phys.
(2014), 141, pp. 014108. , 1029 Acc. Chem. Res.
(2014), 47, pp. 2828. , 674 J. Chem. Phys.
(2016), 144, pp. 164105. and the fragment molecular orbital method, 606 Chem. Phys. Lett.
(1999), 313, pp. 701. for decomposing large clusters into small numbers of monomers, facilitating larger calculations.
TDDFT for molecular interactions [TDDFT(MI)], an excited-state extension of SCF MI that offers
a reduced-cost way to compute excited states in molecular clusters, crystals, and
J. Chem. Phys.
(2015), 143, pp. 034106. , 739 J. Chem. Theory Comput.
(2016), 12, pp. 157. , 487 Acc. Chem. Res.
(2016), 49, pp. 931.
Other fragment-based approaches in Q-Chem include:
Fragment-based approaches to diabatic states and electronic couplings (see Section 10.15.3)