Floating Spherical Gaussian Orbital Model of Molecular Structure. I. Computational Procedure. LiH as an Example

Frost, Arthur A.

doi:10.1063/1.1701524

Cited by 335 publications

(65 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1 Aiming at achieving computational efficiency, a variety of methods based on localized orbitals was developed starting with Special Issue: 2012 Quantum Chemistry Received: March 27, 2011 3 in 1965 in their Group SCF (self-consistent field) method suggested defining molecular orbital groups to reduce the scaling of SCF. Christoffersen and co-workers 4À14 employed localized molecular orbitals (LMOs) and floating spherical Gaussian orbitals (FSGO) 15 to separate the subdensity matrices of fragments that are then summed to obtain the total density and (thereby) desired properties. The method has been applied with success to many species, including molecules of biological importance.…”

Section: Introductionmentioning

confidence: 99%

Fragmentation Methods: A Route to Accurate Calculations on Large Systems

et al. 2011

View full text Add to dashboard Cite

Theoretical chemists have always strived to perform quantum mechanics (QM) calculations on larger and larger molecules and molecular systems, as well as condensed phase species, that are frequently much larger than the current state-of-the-art would suggest is possible. The desire to study species (with acceptable accuracy) that are larger than appears to be feasible has naturally led to the development of novel methods, including semiempirical approaches, reduced scaling methods, and fragmentation methods. The focus of the present review is on fragmentation methods, in which a large molecule or molecular system is made more computationally tractable by explicitly considering only one part (fragment) of the whole in any particular calculation. If one can divide a species of interest into fragments, employ some level of ab initio QM to calculate the wave function, energy, and properties of each fragment, and then combine the results from the fragment calculations to predict the same properties for the whole, the possibility exists that the accuracy of the outcome can approach that which would be obtained from a full (nonfragmented) calculation. It is this goal that drives the development of fragmentation methods. Disciplines Chemistry CommentsReprinted (adapted) with permission from Chemical Reviews 112 (2012): 632,

show abstract

Section: Introductionmentioning

confidence: 99%

Fragmentation Methods: A Route to Accurate Calculations on Large Systems

et al. 2011

View full text Add to dashboard Cite

show abstract

“…The parameters are the same for all electrons, and for all systems studied (4). eFF may be viewed as an elaboration of fermionic molecular dynamics methods (7,8), using a Pauli potential accurate enough that condensed systems with Z > 1 can be described; or as an approximate and time-dependent version of ab initio floating spherical Gaussian orbital (FSGO) theory (9), with exchange energy estimated as a pairwise sum.…”

mentioning

confidence: 99%

Mechanisms of Auger-induced chemistry derived from wave packet dynamics

Goddard

2009

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

To understand how core ionization and subsequent Auger decay lead to bond breaking in large systems, we simulate the wave packet dynamics of electrons in the hydrogenated diamond nanoparticle C 197 H 112 . We find that surface core ionizations cause emission of carbon fragments and protons through a direct Auger mechanism, whereas deeper core ionizations cause hydrides to be emitted from the surface via remote heating, consistent with results from photon-stimulated desorption experiments [Hoffman A, Laikhtman A, (2006) J Phys Condens Mater 18:S1517-S1546]. This demonstrates that it is feasible to study the chemistry of highly excited large-scale systems using simulation and analysis tools comparable in simplicity to those used for classical molecular dynamics.electron force field | fermionic molecular dynamics | floating Gaussian orbitals G reat uncertainties remain concerning how highly excited states (∼100 eV) induced by energetic photons, electrons, ions, or plasmas induce chemical processes at surfaces (1), particularly in large covalent systems (2) relevant to semiconductor fabrication (3). To determine the electron dynamics and atomic mechanisms involved in large-scale highly excited processes, we have developed the electron force field (eFF), a molecular dynamics model that includes electrons. We previously used eFF to compute the thermodynamic properties of warm dense hydrogen, and found excellent agreement with high-level theory, as well as both static compression and dynamic shock experiments (4).We report now the application of eFF to study Auger processes in a hydrogenated diamond nanoparticle C 197 H 112 (Fig. 1A). In the Auger process, ionization of a core electron leads to the collapse of a valence electron into the core hole, together with the ejection of another valence electron, all over several femtoseconds (5). During and after this time, secondary processes occur, causing protons, hydrides, and other species to desorb from hydrogen-terminated surfaces (1). We study the coupled electron-nuclear dynamics of both the primary Auger and accompanying secondary processes, ionizing core electrons both at the diamondoid surface and at different depths below the surface. In this way, we determine how the distance over which an Auger excitation relaxes and propagates affects the energies of electrons and composition of atomic species desorbed from the surface.In eFF, all electrons, valence and core, are modeled as spherical Gaussian wave packets:while nuclei are modeled as classical charged particles moving in the mean field of the electrons. The positions x i and sizes s i of the electrons are continuously variable, giving them the flexibility to participate in covalent, ionic, multicenter, and even metallic bonding; p x,i and p s,i are the corresponding conjugate momenta. This description is well-suited for representing highly excited systems, where electron density maxima and spreads may be distorted from equilibrium positions and values.Substituting the above expression into the time-dependent Schr...

show abstract

“…Since its introduction by Frost [1] and its adaptation by others (Preuss [2], Blustin and Linnett [3], Christoffersen [4], Ford et al [5]) the floating spherical gaussian orbital form of wave function has proved to be a vivid and versatile addition to the armory of theoretical methods. In its original form the minimum number of spherical gaussian was used to set up a determinantal wave function and, to compensate for this small basis set, the positions and exponents of all functions were optimized.…”

Section: Introductionmentioning

confidence: 99%

Floating s and p-type gaussian orbitals

Brailsford

Hall

Hemming

1975

Chemical Physics Letters

View full text Add to dashboard Cite

A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk COLOPHONThe attached paper is another in my series of experiments to see how long it takes me to re-build electronic versions of my published early papers as properly re-typeset 'PDF Normal' rather than just as a bitmap scan.This particular paper appeared in the journal "Chemical Physics Letters" (Elsevier) in 1975. The canonical published version is available online (to subscribers, or for one-off purchase) as a scanned bitmap PDF via: http://www.sciencedirect.com/ The text was acquired by scanning the paper from an offprint and then using Readiris OCR on the resulting TIFF files. The paper was then re-typeset using UNIX troff suite to set up the correct typeface (Times) and to get the line and page breaks as accurate as possible. The tables were re-set using the tbl pre-processor for troff.The time taken to build this paper (over several lunchtimes …) to a reconstituted 'final draft' form was about 4 hours. The advantages of including a small number of p-type gaussian functions in a floating spherical gaussian orbital calculation are pointed out and illustrated by calculations on molecules which previously have proved to be troublesome. These include molecules such as F 2 with multiple lone pairs and C 2 H 2 with multiple bonds. A feature of the results is the excellent correlation between the orbital energies and those of a double zeta calculation reported by Snyder and Basch.

show abstract

Floating Spherical Gaussian Orbital Model of Molecular Structure. I. Computational Procedure. LiH as an Example

Cited by 335 publications

References 44 publications

Fragmentation Methods: A Route to Accurate Calculations on Large Systems

Fragmentation Methods: A Route to Accurate Calculations on Large Systems

Mechanisms of Auger-induced chemistry derived from wave packet dynamics

Floating s and p-type gaussian orbitals

Contact Info

Product

Resources

About