Hydrogen-bonded and van der Waals complexes studied by a Gaussian density functional method. The case of (HF)2, ArHCl and Ar2HCl systems (original) (raw)
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. Ž . Density functional theory DFT calculations with B3LYP exchange-correlation functional and using 6-31 qqG d,p Ž . basis functions have been performed on weakly bound hydrogen bonded complexes between HX X s F,Cl and alkenes and Ž . alkynes, such as C H , C HX X s H,F,Cl , C H and allene. Calculations have also been carried out at MP2 s full level 2 4 2 4 2 of theory and using the same basis set as mentioned above for comparison with the DFT results. It has been observed that the BSSE uncorrected binding energies obtained from the B3LYP calculations are always lower than the corresponding MP2 results whereas opposite trend has been observed after BSSE correction. Hydrogen bond lengths obtained from MP2 and B3LYP calculations differ insignificantly. The H-X frequency shift due to complex formation has been well reproduced by the B3LYP method. q 1998 Elsevier Science B.V. All rights reserved. 0301-0104r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 3 0 1 -0 1 0 4 9 8 0 0 1 1 1 -6
Ab initio calculation of the structure and infrared spectra of the van der Waals complex H 2 O·F 2
Journal of Molecular Structure: THEOCHEM
The equilibrium structures, binding energies and infrared spectra were computed using the ab initio molecular orbital theory for the weakly bonded van der Waals complex H 2 O´F 2. The most stable state was found to possess an effectively planar (as de®ned by Cooke et al. (Angew. Chem., Int. Ed. Engl., 36 (1997) 129)) C s structure with the monomers bonded through the Lewis acid-base type interaction. The zero-point HHO inverting motion could overcome the low barrier of a planar con-®guration and as a result, produces the spectroscopic features observed in the previous microwave measurement. Several intense far infrared vibrational modes were predicted. A considerable uncertainty, arising from the ill-represented harmonic force ®eld presumed by the ab initio theory, was identi®ed for the vibrational analysis. Finally, the quartic centrifugal distortion constants were estimated. Published by Elsevier Science B.V.
Density functional studies of hydrogen-bonded systems
Chemical Physics, 2001
A dielectric continuum approach (SCIPCM) in the framework of density functional theory has been applied to study the structures, energetics and vibrational spectra of hydrogen-bonded H 2 O±CO and H 2 O±OC complexes in a non-polar solvent. The dielectric constants for Ar (1.63), Kr (1.83) and Xe (2.19) were used in order to mimic the low-temperature matrix isolation experiments. We have found that calculations which include a dielectric reaction ®eld around the complexes are able to reproduce the experimentally observed spectral changes. The correction of the calculated interaction energy for the basis set superposition error is discussed in the framework of the self-consistent reaction ®eld approach. Ó
The Journal of Chemical Physics, 2008
Density functional theory ͑DFT͒ in the commonly used local density or generalized gradient approximation fails to describe van der Waals ͑vdW͒ interactions that are vital to organic, biological, and other molecular systems. Here, we propose a simple, efficient, yet accurate local atomic potential ͑LAP͒ approach, named DFT+ LAP, for including vdW interactions in the framework of DFT. The LAPs for H, C, N, and O are generated by fitting the DFT+ LAP potential energy curves of small molecule dimers to those obtained from coupled cluster calculations with single, double, and perturbatively treated triple excitations, CCSD͑T͒. Excellent transferability of the LAPs is demonstrated by remarkable agreement with the JSCH-2005 benchmark database ͓P. Jurečka et al. Phys. Chem. Chem. Phys. 8, 1985 ͑2006͔͒, which provides the interaction energies of CCSD͑T͒ quality for 165 vdW and hydrogen-bonded complexes. For over 100 vdW dominant complexes in this database, our DFT+ LAP calculations give a mean absolute deviation from the benchmark results less than 0.5 kcal/ mol. The DFT+ LAP approach involves no extra computational cost other than standard DFT calculations and no modification of existing DFT codes, which enables straightforward quantum simulations, such as ab initio molecular dynamics, on biomolecular systems, as well as on other organic systems.
Journal of Computational Chemistry, 2007
Standard density functional theory (DFT) is augmented with a damped empirical dispersion term. The damping function is optimized on a small, well balanced set of 22 van der Waals (vdW) complexes and verified on a validation set of 58 vdW complexes. Both sets contain biologically relevant molecules such as nucleic acid bases. Results are in remarkable agreement with reference high-level wave function data based on the CCSD(T) method. The geometries obtained by full gradient optimization are in very good agreement with the best available theoretical reference. In terms of the standard deviation and average errors, results including the empirical dispersion term are clearly superior to all pure density functionals investigated-B-LYP, B3-LYP, PBE, TPSS, TPSSh, and BH-LYPand even surpass the MP2/cc-pVTZ method. The combination of empirical dispersion with the TPSS functional performs remarkably well. The most critical part of the empirical dispersion approach is the damping function. The damping parameters should be optimized for each density functional/basis set combination separately. To keep the method simple, we optimized mainly a single factor, s R , scaling globally the vdW radii. For good results, a basis set of at least triple-quality is required and diffuse functions are recommended, since the basis set superposition error seriously deteriorates the results. On average, the dispersion contribution to the interaction energy missing in the DFT functionals examined here is about 15 and 100% for the hydrogen-bonded and stacked complexes considered, respectively.
Journal of Chemical Theory and Computation, 2007
The geometries, interaction energies, and vibrational frequencies of a series of n-alkane dimers up to dodecane have been calculated using density functional theory (DFT) augmented with an empirical dispersion energy term (DFT-D). The results obtained from this method for ethane to hexane dimers are compared with those provided by the MP2 level of theory and the combined Gaussian-3 approach with CCSD(T) being the highest correlation method [G3(CCSD(T))]. Two types of dimer isomers have been studied. The most stable isomers have the two carbon chains in parallel planes, whereas the second ones have the two carbon chains in the same plane. Butane is found to be the shortest carbon chain to form dimers with similar properties, that is, a constant average distance between the monomer carbon skeletons, a similar increment per CH 2 unit for the dimer interaction energy, and comparable dimer symmetric stretching frequencies. The values and trends obtained from the DFT-D approach agree very well with those obtained from MP2 for the geometries and vibrational frequencies and from the G3(CCSD(T)) method for the energies, validating the use of DFT-D for the study of large hydrocarbon complexes.
The Journal of Chemical Physics, 2006
The formalism based on the total energy bifunctional ͑E͓ I , II ͔͒ is used to derive interaction energies for several hydrogen-bonded complexes ͑water dimer, HCN-HF, H 2 CO-H 2 O, and MeOH -H 2 O͒. Benchmark ab initio data taken from the literature were used as a reference in the assessment of the performance of gradient-free ͓local density approximation ͑LDA͔͒ and gradient-dependent ͓generalized gradient approximation ͑GGA͔͒ approximations to the exchange-correlation and nonadditive kinetic-energy components of E͓ I , II ͔. On average, LDA performs better than GGA. The average absolute error of calculated LDA interaction energies amounts to 1.0 kJ/ mol. For H 2 CO-H 2 O and H 2 O-H 2 O complexes, the potential-energy curves corresponding to the stretching of the intermolecular distance are also calculated. The positions of the minima are in a good agreement ͑less than 0.2 Å͒ with the reference ab initio data. Both variational and nonvariational calculations are performed to assess the energetic effects associated with complexation-induced deformations of molecular electron densities.
The Journal of chemical …, 2003
We are reporting density functional theory results for the binding energies, structures, and vibrational spectra of (H-Cl)(2-6) and (H-F)(2-10) clusters. The performance of different functionals has been investigated. The properties of HF clusters predicted by hybrid functionals are in good agreement with experimental information. The HCl dimer binding energy DeltaE(e) is underestimated by hybrid functionals. The Perdew and Wang exchange and correlation functional (PW91) result for DeltaE(e) is -9.6 kJ mol(-1), in very good agreement with experiment (-9.5 kJ mol(-1)). However, PW91 overestimates binding energies of larger clusters. Hydrogen bonding cooperativity depends on the cluster size n but reaches a limit for moderately sized clusters (n=8 for HF). The average shift to low frequencies (Deltanu) of the X-H (X=Cl,F) stretching vibration relative to the monomer is in good agreement with experimental data for HF clusters in solid neon. However, some discrepancies with experimental results for HCl clusters were observed. The behavior of Deltanu as a function of the cluster size provides an interesting illustration of hydrogen-bond cooperative effects on the vibrational spectrum. The representation of the electronic density difference shows the rearrangement of the electronic density induced by hydrogen bonding in the clusters and supports the view that hydrogen-bond cooperativity is related to electronic sharing and delocalization.
Hydrogen-Bonding and van der Waals Complexes Studied by ZEKE and REMPI Spectroscopy
Chemical Reviews, 2000
I. Introduction 3999 II. Experimental Methods 4000 A. REMPI Spectroscopy 4000 B. ZEKE Spectroscopy 4002 III. Techniques Employing REMPI and ZEKE Spectroscopy 4003 A. Hole-Burning Spectroscopy 4003 B. Mass-Analyzed Threshold Ionization Spectroscopy 4004 C. Photoinduced Rydberg Ionization 4005 D. IR−UV Double Resonance 4006 E. Stimulated Raman−UV Double Resonance 4006 F. Time-Resolved Studies 4006 IV. Probing the Transition from van der Waals to Hydrogen Bonding: REMPI and ZEKE Spectroscopy of Molecular Complexes 4007 A. Inorganic Complexes 4007 i. (Ar) 2 4007 ii. Ar‚NO 4007 iii. (NO) 2 4007 iv. (NH 3) 2 4008 v. Na‚H 2 O 4008 B. Complexes Containing Aromatic Molecules 4009 i. Rare-Gas−Aromatic Complexes 4009 ii. Inorganic Ligand−Aromatic Complexes 4010 C. Aromatic Hydrogen-Bonding Complexes 4013 i. Conformational Isomerism 4013 ii. IR−UV Double-Resonance Spectroscopy 4014 iii. Excited-State Dynamics of Phenol‚(NH 3) n Clusters 4015 iv. Influence of Secondary Functional Groups on a Hydrogen Bond 4016 V. Concluding Remarks 4019 VI. Acknowledgments 4019 VII. Note Added in Proof 4020 VIII. References 4020