Συστηματική κατασκευή βάσεων ατομικών τροχιακών για τον κβαντοχημικό υπολογισμό ηλεκτρικών ιδιοτήτων μορίων

2012 ◽  
Author(s):  
Κωνσταντίνος Μακρής
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Basis Sets ◽  
Functional Theory ◽  
One Dimensional ◽  
Gaussian Type ◽  
One Dimensional Nanostructures

Σκοπός της παρούσης διδακτορικής διατριβής είναι ο σχεδιασμός, με ταυτόχρονη βελτιστοποίηση ενός ή και δύο ταυτόχρονα εκθετών συναρτήσεων πόλωσης, γκαουσιανών (Gaussian type functions, GTF) συνόλων βάσεων ατομικών τροχιακών (basis sets) μικρού και πολύ μεγάλου μεγέθους για τα διαλογόνα ΧΥ (X = F, Cl, Br, I και Υ = F, Cl, Br, I). Βελτιωμένες βάσεις ατομικών τροχιακών χρησιμοποιήθηκαν περαιτέρω για τον υπολογισμό των ηλεκτρικών πολυπολικών ροπών (διπολική έως δεκαεξαπολική) καθώς και των (υπερ)πολωσιμοτήτων των διαλογόνων XY. Μελετήθηκε επίσης επίδραση του μήκους του δεσμού για όλες τις ανωτέρω ιδιότητες με τη χρήση μεθόδων ab initio και Density Functional Theory (DFT). Οι βάσεις χρησιμοποιήθηκαν επίσης στον ab initio υπολογισμό των ηλεκτρικών ιδιοτήτων προτύπων μονοδιάστατων αλυσίδων-νανοδομών (one-dimensional nanostructures, 1D nanowires) της μορφής FY (Υ= F, Cl, Br, I). Μελετήθηκε η εξέλιξη των ηλεκτρικών ιδιοτήτων τους ως συνάρτηση του αριθμού των δομικών μονάδων.

THEORETICAL CALCULATION OF BOND DISSOCIATION ENERGIES AND HEATS OF FORMATION FOR ALKYL NITRATE AND NITRITE COMPOUNDS WITH DENSITY FUNCTIONAL THEORY AND COMPLETE BASIS SET METHOD

2007 ◽  
Vol 06 (03) ◽  
pp. 449-458 ◽  
Author(s):  
XIAO-HONG LI ◽  
RUI-ZHOU ZHANG ◽  
XIN-LU CHENG ◽  
XIANG-DONG YANG
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Heats Of Formation ◽  
Basis Sets ◽  
Bond Dissociation Energies ◽  
Functional Theory ◽  
Dissociation Energies ◽  
Alkyl Nitrate ◽  
Nitrate And Nitrite

The N – O bond dissociation energies (BDEs) and the heats of formation (HOFs) of alkyl nitrate and nitrite compounds in gas phase at 298.15 K were theoretically calculated. Density functional theory (B3LYP and PBE1PBE) with 6-311+g** and 6-311g** basis sets was employed. It is found that PBE1PBE functional has an average increased BDE of 4.03 kcal/mol from B3LYP functional. What is more, we find the reverse trend in ab initio approach, which is slightly smaller than PBE1PBE. The B3LYP functional is found to be sufficiently reliable to compute the BDEs of alkyl nitrate compounds without the presence of diffusion functions. The BDEs of alkyl nitrite compounds appear to be a constant. The functionals (B3LYP and PBE1PBE) with 6-311g** and 6-311+g** basis sets and CBS-4M ab initio method can all yield good results with respect to the experimental HOFs with the deviation less than 2.0 kcal/mol. As the number of methylene group increases, the HOFs of alkyl nitrate and nitrite compounds increase. In addition, the conclusion of Ventural et al. (J Phys Chem A105:9912, 2001 and Phys Lett245:488, 1995) is confirmed again by our computational results.

Dative versus electron-sharing bonding in N-oxides and phosphane oxides R3EO and relative energies of the R2EOR isomers (E = N, P; R = H, F, Cl, Me, Ph). A theoretical study

2018 ◽  
Vol 20 (17) ◽  
pp. 11856-11866 ◽  
Author(s):  
Tao Yang ◽  
Diego M. Andrada ◽  
Gernot Frenking
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Density Functional ◽  
Theoretical Study ◽  
Basis Sets ◽  
Functional Theory

Quantum chemical calculations using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory using BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have been carried out on the title molecules.

Role of Augmented Basis Sets and Quest for ab Initio Performance/Cost Alternative to Kohn–Sham Density Functional Theory

2019 ◽  
Vol 124 (1) ◽  
pp. 126-134 ◽  
Author(s):  
Marco Martínez González ◽  
F. George D. Xavier ◽  
Jing Li ◽  
Luis A. Montero-Cabrera ◽  
Jose M. Garcia de la Vega ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Basis Sets ◽  
Functional Theory

Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

2019 ◽  
Author(s):  
Kamal Batra ◽  
Stefan Zahn ◽  
Thomas Heine
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Absolute Error ◽  
Time Dependent ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
Framework Materials ◽  
Dependent Density

<p>We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV). </p>

scholarly journals Density Functional Theory and Complete Basis Set Ab Initio Computational Study of Five-, Six-, Seven- and Eight-hydrogen Coordinated Carbon Cations

1999 ◽  
Vol 23 (8) ◽  
pp. 502-503
Author(s):  
Branko S. Jursic
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Basis Set ◽  
Functional Theory ◽  
Complete Basis ◽  
Complete Basis Set ◽  
High Level

High level ab initio and density functional theory studies are performed on highly protonated methane species.

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