Hydrogen-bond strengths in large complexes: Efficient calculations using locally dense basis sets
Graphical abstract
Using larger basis sets on the 1° region (atoms in boxes) than on the rest of the molecule improves predicted H-bond strengths.
Introduction
Hydrogen bonding (H-bonding) is an extremely important interaction in chemistry and plays a central role in determining the structures of biomolecules (DNA, proteins) and supramolecular constructs [1]. Unlike dissociation enthalpies of covalent bonds, which are well-reproduced by conventional density functional theory techniques and moderate basis sets [2], predicting accurate H-bond strengths for extended systems remains a computational challenge [3]. This is the case because small absolute errors resulting from a correlation- or basis set-limited computational treatment are large relative to the strength of H-bonds themselves.
Halkier et al. performed an excellent comprehensive study of the convergence of hydrogen bond strengths determined with the Hartree–Fock (HF), second-order Møller–Plesset (MP2) and coupled-cluster singles and doubles with perturbative triples (CCSD(T)) approaches as a function of size of aug-cc-pVXZ basis sets (X = D, T, Q, 5) [4]. They showed that H-bond energies converge to the basis set limit from above when counterpoise (CP) corrections [5] for basis set superposition effects are included but converge from below when CP corrections are omitted. With MP2 and CCSD(T), the convergence is slow and unsystematic without CP corrections. However, with these corrections the errors from an incomplete description of the electronic cusp conditions dominate and the convergence becomes monotonic. Tsuzuki et al. found similar results on a different set of hydrogen-bonded complexes [6].
The slow convergence of correlated wavefunction energies with basis size necessitates the use of large basis sets and CP corrections in order to obtain accurate H-bond strengths. Fortunately, the systematic convergence of CP-corrected H-bond strengths can be exploited to reduce the computational costs associated with calculating H-bond strengths close to the basis set limit. One such approach involves the use of basis set extrapolations. For example, Martin’s [7] simple two-point basis set extrapolation of the formgreatly improves agreement with basis set limit values. This technique extrapolates relative energies (ΔE), such as H-bond energies, to the basis set limit based on values obtained using correlation consistent basis sets and the cardinal numbers (X) of those basis sets. However, for large chemical systems it is often impractical to perform even the aug-cc-pVTZ calculation needed for the lowest level (TZ–DZ or 3-2) extrapolation. One approach to deal with this problem is to use locally dense basis sets (LDBS).
The LDBS approach became popular in NMR calculations after Chestnut’s group demonstrated its utility in computing chemical shifts in large molecules. They showed that such calculations could be performed more quickly and with little loss in accuracy by applying large basis sets only on the NMR chromophores and small basis sets on the other atoms in the molecule [8], [9]. Later, we showed that this approach could be used in a wide range of thermochemical applications including bond dissociation enthalpies, activation energies, proton/electron affinities, solvation energies, and for a limited set of H-bond strengths with little or no loss in accuracy [10]. In our work, we used a large basis set to describe the atoms involved in the region or regions of chemical interest and treated the rest of the system with smaller basis sets or a series of smaller basis sets. We also provided some guidance for applying LDBS to chemical systems of varying complexity. LDBS calculations have much shorter run times than fully balanced large basis set calculations and can alleviate convergence difficulties and hardware limitations.
In this work, we present a more detailed study of the suitability of the LDBS approach for calculating H-bond strengths with the B971 [11] density functional and MP2 methods. In this context, we also examine the effectiveness of the LDBS approach used in conjunction with Martin’s simple, two-point basis set extrapolation scheme [7] with CP corrections. Test calculations are performed on eight small H-bonded complexes. The LDBS approach is then demonstrated by calculating the H-bond strengths of the adenine–thymine (A–T) and cytosine–guanine (C–G) DNA nucleobase pairs and on complexes involving tert-butylmethyl ether with five substituted phenols.
Section snippets
Method of calculation
To test the effectiveness of the LDBS approach in calculating H-bond strengths, we began by considering a set of eight hydrogen-bonded complexes spanning a wide range of interaction energies: ammonia dimer ((NH3)2), water dimer ((H2O)2), formamide–water (OHCNH2–OH2), methanol dimer ((H3COH)2), water–ammonia (OH2–NH3), hydrogen cyanide–hydrogen fluoride (HCN–HF), formamide dimer ((OHCNH2)2), and formic acid dimer ((HCOOH)2). In order to make comparisons of H-bond strengths as meaningful as
Density functional theory H-bond strengths
We begin by considering the CP-corrected balanced basis set B971 BEs for the set of eight small H-bonded complexes. These data are presented in Table 1. The B971 binding energies converge rapidly to the basis set limit, in a manner similar to Hartree–Fock [4]. The aug-cc-pVTZ BEs are in excellent agreement with the BEs at the basis set limit, with a mean absolute error (MAE) of only 0.03 kcal/mol. Increasing the basis set to aug-cc-pVQZ lowers the MAE to 0.00 kcal/mol.
Also listed in Table 1 are
Conclusions
We showed that the use of locally dense basis sets with CP-corrections and basis set extrapolation is an efficient method to obtain BEs of hydrogen-bonded complexes in good agreement with basis set limit values. To be very effective, LDBS calculations should be used for geometry optimizations of the H-bonded complexes as well. Our tests indicate that there is excellent agreement between the LDBS and balanced basis set geometries provided that appropriate complex partitioning is performed.
We
Acknowledgements
We are grateful to T. Kubar and P. Hobza for kindly providing us with calculated structures for the A–T and C–G nucleobase complexes. G.A.D. thanks the Centre for Excellence in Integrated Nanotools (University of Alberta) for access to computational resources.
References (23)
Chem. Phys. Lett.
(1996)- et al.
Chem. Phys. Lett.
(2006) - et al.
Chem. Phys. Lett.
(1993) - et al.
J. Am. Chem. Soc.
(2002) - et al.
J. Phys. Chem. A
(2003) - et al.
Phys. Chem. Chem. Phys.
(2006) - et al.
J. Chem. Phys.
(1999) - et al.
Mol. Phys.
(1970) - et al.
J. Chem. Phys.
(1999) - et al.
J. Comput. Chem.
(1989)
J. Comput. Chem.
Cited by (12)
Structural and energetic quantum chemical investigations into how the bioactive thiazolidinedione and rhodanine scaffolds interact with cytosine to form part of DNA
2018, Computational and Theoretical ChemistryCitation Excerpt :The strength of the hydrogen bond lies between 1 and 2 kJ/mol (very weak) and 161.5 kJ/mol (very strong) [5,6]. Hydrogen bonding interactions are also mainly electrostatic with some contribution of charge transfer and polarization in nature [7–13]. Many bioactive molecules could act as both hydrogen bond acceptor and donor, and thus investigations including the effects of hydrogen bond interactions on the properties, activity and nature of the interactions of biologically active molecules are of great interest and much computational and experimental research works has been focused on them [14–35].
A quantum chemical insight to intermolecular hydrogen bonding interaction between cytosine and nitrosamine: Structural and energetic investigations
2016, Journal of Molecular StructureCitation Excerpt :The Hydrogen bonding type in many of DNA molecules is as N–H⋯O and N–H⋯N. Because of theirs importance, they have been widely investigated. The results of investigations indicated that the nature of hydrogen bonding interactions is mainly electrostatic with some contribution of charge transfer and polarization [4–10]. Hydrogen bonding also stabilizes the structures of biological molecules such as proteins and nucleic acids.
A systematic study on hydrogen bonding interaction between formamide and cytosine
2010, Journal of Molecular Structure: THEOCHEMDFT Investigation of a Charge-Transfer Complex Formation Between p-Phenylenediamine and 3,5-Dinitrosalicylic Acid
2019, Journal of Structural ChemistryUnderstanding the Many-Body Basis Set Superposition Error: Beyond Boys and Bernardi
2018, Journal of Chemical Theory and ComputationPerformance of conventional and dispersion-corrected density-functional theory methods for hydrogen bonding interaction energies
2013, Physical Chemistry Chemical Physics
- 1
Present address: Department of Chemistry, Dalhousie University, Halifax, Canada NS B3H 4J3.