Optimization of parameters for semiempirical methods V: Modification of NDDO approximations and application to 70 elements

Stewart, James J. P.

doi:10.1007/s00894-007-0233-4

Cited by 3,313 publications

(2,836 citation statements)

References 35 publications

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“…This is not to say that the semiempirical development community has stagnated in groupthink, we mean only to highlight the realities that drive the direction of model development. The designer of a next-generation semiempirical model will do so under the influence of one of two prejudices: (1) current models are "fine as they are" and need only minor modifications to their parameters or functional forms; or (2) the parameters of the original semiempirical models have now been sufficiently trained [19], and the parametric freedom of the ad hoc functions used to replace the model's missing physics has now been sufficiently extended [ 15 ], that a further significant advance will need to address the fundamental approximations of the method in some inherently new way [23][24][25]. The former option is attractive because it promises to offer instant gratification and can be more easily demonstrated to be fast and accurate.…”

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confidence: 99%

Density-functional expansion methods: grand challenges

Giese¹,

York²

2012

Highlights in Theoretical Chemistry

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We discuss the source of errors in semiempirical density functional expansion (VE) methods. In particular, we show that VE methods are capable of well-reproducing their standard Kohn-Sham density functional method counterparts, but suffer from large errors upon using one or more of these approximations: the limited size of the atomic orbital basis, the Slater monopole auxiliary basis description of the response density, and the one-and two-body treatment of the coreHamiltonian matrix elements. In the process of discussing these approximations and highlighting their symptoms, we introduce a new model that supplements the second-order density-functional tight-binding model with a self-consistent charge-dependent chemical potential equalization correction; we review our recently reported method for generalizing the auxiliary basis description of the atomic orbital response density; and we decompose the first-order potential into a summation of additive atomic components and many-body corrections, and from this examination, we provide new insights and preliminary results that motivate and inspire new approximate treatments of the core-Hamiltonian.

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confidence: 99%

Density-functional expansion methods: grand challenges

Giese¹,

York²

2012

Highlights in Theoretical Chemistry

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“…Lithium atoms were placed between two such porous graphene sheets, and the atom coordinates and supercell lattice constants were optimized using PM6-D2 [87,88] Following the discussion above, it is likely that similar slight geometry differences among the other pores contribute to the deviations in barrier heights.…”

Section: Potential Energy Surface Construction By Ab Initio Methodsmentioning

confidence: 99%

Deep nuclear resonant tunneling thermal rate constant calculations

Mandrà

Valleau

Ceotto

2013

Int J of Quantum Chemistry

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A fast and robust time‐independent method to calculate thermal rate constants in the deep resonant tunneling regime for scattering reactions is presented. The method is based on the calculation of the cumulative reaction probability which, once integrated, gives the thermal rate constant. We tested our method with both continuous (single and double Eckart barriers) and discontinuous first derivative potentials (single and double rectangular barriers). Our results show that the presented method is robust enough to deal with extreme resonating conditions such as multiple barrier potentials. Finally, the calculation of the thermal rate constant for double Eckart potentials with several quasi‐bound states and the comparison with the time‐independent log‐derivative method are reported. An implementation of the method using the Mathematica Suite is included in the Supporting Information. © 2013 Wiley Periodicals, Inc.

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“…The full geometrical optimization for ground state of cefixima and aminobenzylpenicillin drug inhibitors has been performed by employing the parametric method (PM6) 25,26 because this routine is highly dependable for estimating the electronic properties of molecules which have bulk numbers of orbitals and electrons. Its many modifications form other semi-empirical approximations allowed for seventy elements 25 to be parameterized, such as core-core interactions and the more accurate results involved the d-orbitals for the main group elements. The quantum chemical parameters were calculated for optimized structures of the drug inhibitors e.g.…”

Section: Theoretical Calculationsmentioning

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A Study into the Corrosion Inhibition of Carbon Steel in Acidic Medium Using Eco-Friendly Compounds

2017

Irq. Nat. J. Chem.

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The corrosion inhibition effects of cefixima and aminobenzylpenicillin drug inhibitors in 0.05M deaerated sulfuric acid solution for carbon steel have been studied by using electrochemical techniques and quantum chemical calculations as well as scanning electron microscope (SEM). It is observed from the experimental findings that both compounds perform as good inhibitors and behave according to mixed type inhibitor in terms of their inhibitory action. Additionally, it was found the percentage of corrosion inhibition become maximal when the concentrations of the cefixima and aminobenzylpenicillin inhibitors are increased. The influence of temperature on the corrosion of carbon steel has been investigated and the activation energy values estimated. The corrosion efficiency decreases with increasing the temperature range. The parameters of thermodynamic have been determined and indicate that the adsorption mechanism follows the Langmuir isotherm model and forms a protective layer on carbon steel surface electrode, which was characterized by scanning electron microscope measurements, to prevent a corrosion process. Quantum chemical calculations have been performed to provide evidence for corrosion inhibition according to the chemical structures of the cefixima and aminobenzylpenicillin drug inhibitors.

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Optimization of parameters for semiempirical methods V: Modification of NDDO approximations and application to 70 elements

Cited by 3,313 publications

References 35 publications

Density-functional expansion methods: grand challenges

Density-functional expansion methods: grand challenges

Deep nuclear resonant tunneling thermal rate constant calculations

A Study into the Corrosion Inhibition of Carbon Steel in Acidic Medium Using Eco-Friendly Compounds

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