Quasiatomic orbitals for<i>ab initio</i>tight-binding analysis

Qian, Xiaofeng; Li, Ju; Qi, Liang; Wang, Cai Zhuang; Chan, Tzu-Liang; Yao, Yao; Ho, Kai Ming; Yip, Sidney

doi:10.1103/physrevb.78.245112

Cited by 110 publications

(131 citation statements)

References 72 publications

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“…Charges of individual atoms of optimized structures were determined by transforming the converged wavefunctions into a set of localized quasi-atomic orbitals (QUAMBO) (43)(44)(45)(46). from NH 4 + decomposition (6)] are proportional to the alkene pressure (10-500 kPa; 503 K) (Fig.…”

Section: Experimental Methodsmentioning

confidence: 99%

Stability of bound species during alkene reactions on solid acids

Sarazen

Iglesia

2017

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

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This study reports the thermodynamics of bound species derived from ethene, propene, n-butene, and isobutene on solid acids with diverse strength and confining voids. Density functional theory (DFT) and kinetic data indicate that covalently bound alkoxides form C-C bonds in the kinetically relevant step for dimerization turnovers on protons within TON (0.57 nm) and MOR (0.67 nm) zeolitic channels and on stronger acids HPW (polyoxometalate clusters on silica). Turnover rates for mixed alkenes give relative alkoxide stabilities; the respective adsorption constants are obtained from in situ infrared spectra. Tertiary alkoxides (from isobutene) within larger voids (MOR, HPW) are more stable than less substituted isomers but are destabilized within smaller concave environments (TON) because framework distortions are required to avoid steric repulsion. Adsorption constants are similar on MOR and HPW for each alkoxide, indicating that binding is insensitive to acid strength for covalently bound species. DFT-derived formation free energies for alkoxides with different framework attachments and backbone length/structure agree with measurements when dispersion forces, which mediate stabilization by confinement in host-guest systems, are considered. Theory reveals previously unrecognized framework distortions that balance the C-O bond lengths required for covalency with host-guest distances that maximize van der Waals contacts. These distortions, reported here as changes in O-atom locations and dihedral angles, become stronger for larger, more substituted alkoxides. The thermodynamic properties reported here for alkoxides and acid hosts differing in size and conjugate-anion stability are benchmarked against DFT-derived free energies; their details are essential to design hostguest pairs that direct alkoxide species toward specific products.zeolites | alkene adsorption | heterogeneous catalysis | density functional theory H ydrocarbon reactions on solid Brønsted acids often involve bound alkene-derived intermediates. Their reactivity and selectivity in C-C bond formation and cleavage and in hydrogen transfer reactions depend on their thermodynamic properties, which reflect, in turn, the properties of the conjugate anion and of the confining voids in microporous solid acids. Weakly bound adsorbed alkanes interact with void walls via dispersion forces at low temperatures without molecular transformations; their unreactive nature allows accurate assessments of their binding properties (1-4). Alkenes interact with protons via H bonding or π-interactions, as well as by proton transfer from strong acids to form alkoxides; the intermediate between these states is a positively charged carbenium ion. The thermodynamics of alkoxide formation remain uncertain because of their very fast oligomerization and β-scission reactions (5, 6), thus requiring indirect inferences from kinetic, spectroscopic, or theoretical methods. This uncertainty is particularly prevalent in isobutene-derived species, for which steric effects may disfavor the f...

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Section: Experimental Methodsmentioning

confidence: 99%

Stability of bound species during alkene reactions on solid acids

Sarazen

Iglesia

2017

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

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“…In the past several years, extensive first-principles calculations based on density functional theory have also been carried out to study the adsorption properties of various metals on graphene in order to gain detailed insights into the interaction of the metals with graphene . The first-principles DFT plane-wave basis calculations have also been combined with quasi-atomic minimal basis orbitals (QUAMBOs) scheme [104][105][106] and Mulliken charge analysis to evaluate the amount of electron transfer between the adatoms and the graphene layer [71][72][73][74][75][76][77][78]. The degree of covalent bonding is also studied through Mayer bond order [107] analysis based on the QUAMBOs.…”

Section: Interactions Between Metal Adatoms and Graphenementioning

confidence: 99%

Metals on Graphene: Interactions, Growth Morphology, and Thermal Stability

et al. 2013

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Graphene, a single atomic layer of graphite, has been a material of recent intensive studies due to its novel electronic and structural properties and its potential applications in the emerging area of carbon-based electronic devices. Metal on graphene growth is one of the current research interests, aiming at improving and manipulating the electronic and magnetic properties of graphene through metal atom adsorption or doping to meet various requirements in device applications. In this paper, we will give an overview of recent experimental and computational investigation of interaction, growth morphology, and thermal stability of various metals on graphene grown on 6H-SiC(0001) substrate.

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“…44. The target NAOs are given by ⌽ Alm ͑r͒ = Al ͑r͒Y lm ͑r͒, where Al is a modified Gaussian which vanish outside a specified cutoff radius and Y lm are the spherical harmonics corresponding to the valence of atom A.…”

Section: A Augmented Wannier-function Basismentioning

confidence: 99%

Fully self-consistent GW calculations for molecules

2010

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We calculate single-particle excitation energies for a series of 34 molecules using fully self-consistent GW, one-shot G 0 W 0 , Hartree-Fock ͑HF͒, and hybrid density-functional theory ͑DFT͒. All calculations are performed within the projector-augmented wave method using a basis set of Wannier functions augmented by numerical atomic orbitals. The GW self-energy is calculated on the real frequency axis including its full frequency dependence and off-diagonal matrix elements. The mean absolute error of the ionization potential ͑IP͒ with respect to experiment is found to be 4.4, 2.6, 0.8, 0.4, and 0.5 eV for DFT-PBE, DFT-PBE0, HF, G 0 W 0 ͓HF͔, and self-consistent GW, respectively. This shows that although electronic screening is weak in molecular systems, its inclusion at the GW level reduces the error in the IP by up to 50% relative to unscreened HF. In general GW overscreens the HF energies leading to underestimation of the IPs. The best IPs are obtained from one-shot G 0 W 0 calculations based on HF since this reduces the overscreening. Finally, we find that the inclusion of core-valence exchange is important and can affect the excitation energies by as much as 1 eV.

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Quasiatomic orbitals forab initiotight-binding analysis

Cited by 110 publications

References 72 publications

Stability of bound species during alkene reactions on solid acids

Stability of bound species during alkene reactions on solid acids

Metals on Graphene: Interactions, Growth Morphology, and Thermal Stability

Fully self-consistent GW calculations for molecules

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