Reaction Of Diamond Surfaces With Halogen-Containing Species

1995 ◽  
Vol 416 ◽  
Author(s):  
K. Larsson
Keyword(s):  
Adsorption Energy ◽  
Growth Process ◽  
Initial Step ◽  
Quantum Mechanical ◽  
Structural Configuration ◽  
Structural Comparison ◽  
Diamond Surfaces ◽  
Mechanical Methods ◽  
Adsorption Processes ◽  
Adsorption Energies

ABSTRACTAn energetic and structural comparison has been made concerning adsorption processes on a diamond (111) surface from a hydrogen (H)-, halogen (X)- or H/X-carrying carbon precursors. The halogens X examined were F, Cl and Br. The quantum mechanical methods used in the investigation were the ab initio MO method as well as the LDA method. F, Cl, and H, were all shown to be able to sustain the sp3 structural configuration of the surface carbon atoms. For Br large sterical hindrances were induced and the diamond (111) surface could not be stabilized. The calculated adsorption energy of CF3 to a H-terminated diamond (111) surface was found to be numerically the largest one (489 kJ/mol on the MP2 level of theory) in comparison to the other adsorption processes studied in the present investigation. It was, in particular, much larger than the corresponding adsorption energy of CH3 (418 kJ/mol). The calculated adsorption energies do support the initial step in the growth process (adsorption) to be energetically more favourable for systems incorporating a mixture of halogen and hydrogen in the growth vapor than for corresponding systems involving unmixed halogen or hydrogen in the carbon containing precursor.

scholarly journals Interactions between large molecules pose a puzzle for reference quantum mechanical methods

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yasmine S. Al-Hamdani ◽  
Péter R. Nagy ◽  
Andrea Zen ◽  
Dennis Barton ◽  
Mihály Kállay ◽  
...  
Keyword(s):  
Experimental Information ◽  
Quantum Mechanical ◽  
Interaction Energies ◽  
Small Organic Molecules ◽  
Large Molecules ◽  
Reference Information ◽  
Mechanical Methods ◽  
Non Covalent Interactions ◽  
Semi Empirical ◽  
Covalent Interactions

AbstractQuantum-mechanical methods are used for understanding molecular interactions throughout the natural sciences. Quantum diffusion Monte Carlo (DMC) and coupled cluster with single, double, and perturbative triple excitations [CCSD(T)] are state-of-the-art trusted wavefunction methods that have been shown to yield accurate interaction energies for small organic molecules. These methods provide valuable reference information for widely-used semi-empirical and machine learning potentials, especially where experimental information is scarce. However, agreement for systems beyond small molecules is a crucial remaining milestone for cementing the benchmark accuracy of these methods. We show that CCSD(T) and DMC interaction energies are not consistent for a set of polarizable supramolecules. Whilst there is agreement for some of the complexes, in a few key systems disagreements of up to 8 kcal mol−1 remain. These findings thus indicate that more caution is required when aiming at reproducible non-covalent interactions between extended molecules.

scholarly journals A Review on Combination of Ab Initio Molecular Dynamics and NMR Parameters Calculations

2021 ◽  
Vol 22 (9) ◽  
pp. 4378
Author(s):  
Anna Helena Mazurek ◽  
Łukasz Szeleszczuk ◽  
Dariusz Maciej Pisklak
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Small Amplitude ◽  
Ab Initio Molecular Dynamics ◽  
Quantum Mechanical ◽  
Time Step ◽  
Noticeable Effect ◽  
Nmr Parameters ◽  
Mechanical Methods ◽  
Simulation Time

This review focuses on a combination of ab initio molecular dynamics (aiMD) and NMR parameters calculations using quantum mechanical methods. The advantages of such an approach in comparison to the commonly applied computations for the structures optimized at 0 K are presented. This article was designed as a convenient overview of the applied parameters such as the aiMD type, DFT functional, time step, or total simulation time, as well as examples of previously studied systems. From the analysis of the published works describing the applications of such combinations, it was concluded that including fast, small-amplitude motions through aiMD has a noticeable effect on the accuracy of NMR parameters calculations.

scholarly journals New Approach for Correcting Noncovalent Interactions in Semiempirical Quantum Mechanical Methods: The Importance of Multiple-Orientation Sampling

2021 ◽  
Vol 17 (9) ◽  
pp. 5556-5567
Author(s):  
Sergio Pérez-Tabero ◽  
Berta Fernández ◽  
Enrique M. Cabaleiro-Lago ◽  
Emilio Martínez-Núñez ◽  
Saulo A. Vázquez
Keyword(s):  
Noncovalent Interactions ◽  
Quantum Mechanical ◽  
New Approach ◽  
Mechanical Methods

Quantum Mechanical Methods for the Investigation of Metalloproteins and Related Bioinorganic Compounds

2014 ◽  
pp. 207-268 ◽  
Author(s):  
Luca Bertini ◽  
Maurizio Bruschi ◽  
Ugo Cosentino ◽  
Claudio Greco ◽  
Giorgio Moro ◽  
...  
Keyword(s):  
Quantum Mechanical ◽  
Mechanical Methods

scholarly journals Studying the excited electronic states of guanine rich DNA quadruplexes by quantum mechanical methods: main achievements and perspectives

2020 ◽  
Vol 19 (4) ◽  
pp. 436-444 ◽  
Author(s):  
Lara Martínez-Fernández ◽  
Luciana Esposito ◽  
Roberto Improta
Keyword(s):  
Electronic States ◽  
Quantum Mechanical ◽  
Excited Electronic States ◽  
Mechanical Methods ◽  
Dna Quadruplexes

Calculations are providing more and more useful insights into the interaction between light and DNA quadruplexes.

scholarly journals Unprecedented η3-Coordination and Functionalization of the 2-Phosphaethynthiolate Anion at Lanthanum(III)

2021 ◽  
Author(s):  
Fabian A. Watt ◽  
Lukas Burkhardt ◽  
Roland Schoch ◽  
Stefan Mitzinger ◽  
Matthias Bauer ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Coordination Mode ◽  
Quantum Mechanical ◽  
Structural Comparison ◽  
Anion Complex ◽  
Steric Factors ◽  
Group 15 ◽  
Detailed Reaction Mechanism ◽  
The Ideal

We present the unprecedented <i>η</i>3-coordination of the 2-phosphaethynthiolate anion in the complex (PN)<sub>2</sub>La(SCP) (<b>2</b>) [PN = N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide)]. Structural comparison with dinuclear thiocyanate bridged (PN)<sub>2</sub>La(<i>μ</i>-1,3-SCN)<sub>2</sub>La(PN)<sub>2</sub> (<b>3</b>) and azide bridged (PN)<sub>2</sub>La(<i>μ</i>-1,3-N3)<sub>2</sub>La(PN)<sub>2</sub> (<b>4</b>) complexes indicates that the [SCP]<sup>–</sup> coordination mode is mainly governed by electronic, rather than steric factors. Quantum mechanical investigations reveal large contributions of the antibonding π-orbital of the [SCP]<sup>–</sup> ligand to the LUMO of complex <b>2</b>, rendering it the ideal precursor for the first functionalization of the [SCP]<sup>–</sup> anion. Complex <b>2</b> was therefore reacted with CAACs which induced a selective rearrangement of the [SCP]<sup>–</sup> ligand to form the first CAAC stabilized group 15 – group 16 fulminate-type complexes (PN)<sub>2</sub>La{SPC(<sup>R</sup>CAAC)} (<b>5a,b</b>) (R = Ad, Me). A detailed reaction mechanism for the SCP to SPC isomerization is proposed based on DFT calculations.

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