Anticipating π-Bond Dispositions in Cyclic, Even, Classical Hydrocarbons

2011 ◽  
Vol 64 (3) ◽  
pp. 324 ◽  
Author(s):  
Richard F. Langler
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Experimental Results ◽  
New Technique ◽  
Structural Isomers ◽  
Functional Theory ◽  
Singlet States ◽  
Hückel Theory ◽  
A New Technique

A new technique, which employs π-bond placement coefficients, is presented. That technique, in conjunction with a few parameters that are readily available from traditional Hückel theory, permits one to systematically anticipate π-bond placements for optimized lowest-lying singlet states. One may then foresee the relative magnitudes of calculated ΔHf values for selected sets of structural isomers. Structural predictions are compared with parameterization method 3 (PM3) calculations, density functional theory calculations and experimental results. Reasonable expectations for the most stable structure narrow the choice of molecules that may then be scrutinized by more exact computations or by experiment.

From HCOOH to CO on Pd catalyst: theoretical study

2017 ◽  
Vol 95 (10) ◽  
pp. 1081-1084 ◽  
Author(s):  
Yingying Wang ◽  
Zijiao Chen
Keyword(s):  
Density Functional Theory ◽  
Formic Acid ◽  
Density Functional ◽  
Theoretical Study ◽  
Density Functional Theory Calculations ◽  
Experimental Results ◽  
Pd Catalyst ◽  
Co Poisoning ◽  
Functional Theory ◽  
Experimental Findings

The present theoretical and experimental results in the literature for formic acid (HCOOH) oxidation into CO on Pd(111) cannot rationalize the well-known, easy CO poisoning. The present study reexamines HCOOH oxidation on Pd(111) by performing density functional theory calculations. Upon a thorough search, we present a new adsorption configuration of HCOOH on Pd(111). From the calculated energy pathway, we proposed that CO arises from the reduction of the hydrogenation product CO2 and direct dehydration of formic acid during HCOOH oxidation on Pd(111), with latter step being energetically easier. The present theoretical study rationalizes the early experimental findings and provides insights into the deactivation problem of Pd catalyst in the process of HCOOH oxidation.

Is a Non-Transition Element Nitride Ferromagnet Ever Achievable? Indication of the N-N Pairing Instability

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1525-1531 ◽  
Author(s):  
Wojciech Grochala
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Transition Element ◽  
Density Functional Theory Calculations ◽  
Functional Theory

The enthalpy of four polymorphs of CaN has been scrutinized at 0 and 100 GPa using density functional theory calculations. It is shown that structures of diamagnetic calcium diazenide (Ca2N2) are preferred over the cubic ferromagnetic polymorph (CaN) postulated before, both at 0 and 100 GPa.

scholarly journals Tensor-structured algorithm for reduced-order scaling large-scale Kohn–Sham density functional theory calculations

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Chih-Chuen Lin ◽  
Phani Motamarri ◽  
Vikram Gavini
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Density Functional Theory Calculations ◽  
System Size ◽  
Real Space ◽  
Functional Theory ◽  
Reduced Order ◽  
Separable Approximation ◽  
Tensor Basis

AbstractWe present a tensor-structured algorithm for efficient large-scale density functional theory (DFT) calculations by constructing a Tucker tensor basis that is adapted to the Kohn–Sham Hamiltonian and localized in real-space. The proposed approach uses an additive separable approximation to the Kohn–Sham Hamiltonian and an L1 localization technique to generate the 1-D localized functions that constitute the Tucker tensor basis. Numerical results show that the resulting Tucker tensor basis exhibits exponential convergence in the ground-state energy with increasing Tucker rank. Further, the proposed tensor-structured algorithm demonstrated sub-quadratic scaling with system-size for both systems with and without a gap, and involving many thousands of atoms. This reduced-order scaling has also resulted in the proposed approach outperforming plane-wave DFT implementation for systems beyond 2000 electrons.

scholarly journals Polymorphs of Rb3ScF6: X-ray and Neutron Diffraction, Solid-State NMR, and Density Functional Theory Calculations Study

2021 ◽  
Vol 60 (8) ◽  
pp. 6016-6026
Author(s):  
Aydar Rakhmatullin ◽  
Maxim S. Molokeev ◽  
Graham King ◽  
Ilya B. Polovov ◽  
Konstantin V. Maksimtsev ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Neutron Diffraction ◽  
Solid State Nmr ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
X Ray
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