Intermolecular forces via hybrid Hartree–Fock–SCF plus damped dispersion (HFD) energy calculations. An improved spherical model

Douketis, Constantine; Scoles, G.; Marchetti, S.; Zen, M.; Thakkar, Ajit J.

doi:10.1063/1.443345

Cited by 308 publications

(100 citation statements)

References 37 publications

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“…Integrating this term over an estimate for the helium solvation density gave a shift for SF 6 [125] of about one half the observed value of −1.6 cm −1 [14,53] (such an estimate is for the vertical, not adiabatic shift). A sizable fraction of the shift comes from the first solvation shell, for which the use of the long range R −6 terms is not expected to be complete, though there may be a significant cancellation of errors between the neglect of higher order terms and damping of the dispersion series [126]. For molecules with a permanent dipole moment, one also needs to consider the changes in the vibrationally averaged dipole moment.…”

Section: E Shift In Band Originsmentioning

confidence: 99%

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Callegari¹,

Lehmann²,

Schmied³

et al. 2001

The Journal of Chemical Physics

350

459

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In this article, recent developments in HElium NanoDroplet Isolation (HENDI) spectroscopy are reviewed, with an emphasis on the infrared region of the spectrum. We discuss how molecular beam spectroscopy and matrix isolation spectroscopy can be usefully combined into a method that provides a unique tool to tackle physical and chemical problems which had been outside our experimental possibilities. Next, in reviewing the experimental methodology, we present design criteria for droplet beam formation and its seeding with the chromophore(s) of interest, followed by a discussion of the merits and shortcomings of radiation sources currently used in this type of spectroscopy. In a second, more conceptual part of the review, we discuss several HENDI issues which are understood by the community to a varied level of depth and precision. In this context, we show first how a superfluid helium cluster adopts the symmetry of the molecule or complex seeded in it and discuss the nature of the potential well (and its isotropy) that acts on a solute inside a droplet, and of the energy levels that arise because of this confinement. Second, we treat the question of the homogeneous versus inhomogeneous broadening of the spectral profiles, moving after this to a discussion of the rotational dynamics of the molecules and of the surrounding superfluid medium. The change in rotational constants from their gas phase values, and their dependence on the angular velocity and vibrational quantum number are discussed. Finally, the spectral shifts generated by this very gentle matrix are analyzed and shown to be small because of a cancellation between the opposing action of the attractive and repulsive parts of the potential of interaction between molecules and their solvent. The review concludes with a discussion of three recent applications to (a) the synthesis of far-fromequilibrium molecular aggregates that could hardly be prepared in any other way, (b) the study of the influence of a simple and rather homogeneous solvent on large amplitude molecular motions, and (c) the study of mixed 3 He/ 4 He and other highly quantum clusters (e.g., H2 clusters) prepared inside helium droplets and interrogated by measuring the IR spectra of molecules embedded in them. In spite of the many open questions, we hope to convince the reader that HENDI has a great potential for the solution of several problems in modern chemistry and condensed matter physics, and that, even more interestingly, this unusual environment has the potential to generate new sets of issues which were not in our minds before its introduction.

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Section: E Shift In Band Originsmentioning

confidence: 99%

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Callegari¹,

Lehmann²,

Schmied³

et al. 2001

The Journal of Chemical Physics

350

459

View full text Add to dashboard Cite

show abstract

“…In order to overcome this severe deficiency of DFT, two basic strategies have been adopted: on one hand, new density functionals or/and relatively complex schemes have been proposed that in principle allow for a correct treatment of the VdW interactions [1,3,4,5,6,7,8,9], on the other hand several semiempirical approaches [10,11] have been developed where an approximately derived R −6 term, multiplied by a suitable shortrange damping function, is explicitly introduced. Although both these approaches have been somehow successful, neither of them appears to be entirely satisfactory: in fact, the former is generally quite complex and computationally very demanding, compared to a standard DFT calculation, while the latter, based on interatomic C 6 coefficients (actually dependent on the molecular environment of the atoms involved) and empirical fits, turns out to be far from generally applicable because it neglects changes in the atomic polarizabilities (which, in general, are not additive) and should be tailored to the specific system considered.…”

mentioning

confidence: 99%

Van der Waals Interactions in DFT Made Easy by Wannier Functions

2008

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Ubiquitous Van der Waals interactions between atoms and molecules are important for many molecular and solid structures. These systems are often studied from first principles using the Density Functional Theory (DFT). However, the commonly used DFT functionals fail to capture the essence of Van der Waals effects. Many attempts to correct for this problem have been proposed, which are not completely satisfactory because they are either very complex and computationally expensive or have a basic semiempirical character. We here describe a novel approach, based on the use of the Maximally-Localized Wannier functions, that appears to be promising, being simple, efficient, accurate, and transferable (charge polarization effects are naturally included). The results of test applications are presented.

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“…At that point, I saw no reason to let the parameters of the exponential repulsion float free because they could be calculated very precisely in the HartreeFock approximation with a priori methods. Because C 6 values at that time were starting to be well known, we put the variable parameters into C 8 and C 10 and in their damping coefficients (11 …”

Section: Simplifying the Theory Of Intermolecular Forces: The Hfd Potmentioning

confidence: 99%

The Independence of the Junior Scientist's Mind: At What Price?

Scoles

2016

Annu. Rev. Phys. Chem.

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When I was facing the daunting task of recounting my approximately 70 years of scientific career and some aspects of my personal life, I decided to write this autobiographical piece in a "different" way. After a section on the almost bare facts of my life (Section 1), I include several other parts, loosely connected in time, in each of which I make an almost self-contained point, decreasing in this way the need for consistency and coherence in the whole article. I discuss, for example, the importance of original ideas, the independence of junior colleagues, and my work with molecular beams and in nanomedicine. I end by acknowledging those I was lucky enough to learn from in my intellectual development as a research scientist and with a couple of recommendations that may be useful to my junior and not-so-junior colleagues.

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Intermolecular forces via hybrid Hartree–Fock–SCF plus damped dispersion (HFD) energy calculations. An improved spherical model

Cited by 308 publications

References 37 publications

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Helium nanodroplet isolation rovibrational spectroscopy: Methods and recent results

Van der Waals Interactions in DFT Made Easy by Wannier Functions

The Independence of the Junior Scientist's Mind: At What Price?

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