Simulating Electronic Structure of Condensed Adamantane

Diamond and Related Materials, 2004

A self-consistent environment-dependent tight binding method is used to examine electron emission-related properties of hydrogen passivated nano-diamond (ND) particles. For sizes larger than 2.5 nm particle bandgap was found to be equal to the bandgap of bulk diamond. Coulomb potential distributions and electron affinities of clusters were found to be insensitive to the particle size if it exceeds 1.0 nm. Tunneling probabilities for homogeneous and inhomogeneous emission models were estimated. The simulation results indicate that the low emission threshold for hydrogen passivated diamond nano-clusters is due to hydrogen-assisted emission from the edges of small unpassivated islands. Essentially the same mechanism is claimed to be responsible for good emission properties of hydrogen passivated diamond films by Ristein [Diam. Relat. Mater. 9, 1129 (2000)].

Diamond and Related Materials, 2010

We generated and evaluated energetically a very large number of vacancy V n clusters representing nanosize voids or cavities in diamond for n up to 14 using a new generational algorithm. We evaluated the relaxed geometries and energies of these contiguous vacancy clusters using a tight binding density functional theory (TBDFT). For up to n = 7 we generated all possible structures and evaluated their relaxed geometries. For n = 8 through n = 14 we selectively generated a large number of vacancy clusters and obtained highly stable structures and their energies. By analyzing the energy levels and the corresponding orbitals, we identified the surface states of the voids and their symmetries. Significant differences with respect to vacancy clusters in silicon were found. The results were interpreted by finding that certain structures become relatively more stable due to a process we call local graphitization, which can be identified by a tetrahedron of graphitization (TOG), and it can be characterized by elongation of certain carbon-carbon contacts and by the concomitant appearance of new states in the gap. The beginning of graphitization, as indicated by geometrical and energetic descriptors in small stable vacancy clusters, may have a role in the formation mechanisms of various sp 2 hybridized structures in carbons.

Journal of Applied Spectroscopy

We have used the density functional method to model the atomic and electronic structure of diamond nanocrystals passivated by hydrogen atoms and either not containing defects or containing a single [NV]-center. We have shown that in all cases, after relaxation the nanocrystals are formed as diamond-like structures.

IntechOpen eBooks, 2023

In this chapter, we present a study on the electronic properties of diamond carbon, using band structure and density of states calculations. The calculations are based on the use of the grid-based projector-augmented wave (GPAW) and atomic simulation environment (ASE) methods. The main results of our work are the optimization of diamond energy (to À17.57 eV) and the calculation of the gap with the PBE (Perdew, Burke, and Ernzerhof) and the functional hybrid PBE0 hybrid functional, which is about 5.368 eV (the closest value to the value found in the literature). We were also able to reproduce the experimental value of the lattice constant of diamond to within 0.2% for PBE0 and 0.4% for PBE. Our results contribute to the study of the electronic properties of diamond using GPAW and ASE simulation, which is a set of Python modules, designed to facilitate the setup, execution, and analysis of atomic/electronic calculations. This tight integration of ASE and GPAW should be exploited in future research of the electronic properties of diamond, which is one of the most promising materials for the integrated electronic and photonic, radio, optoelectronic, and quantum devices industry. This chapter provides interesting information for the theoretical and experimental communities working in this field.

Journal of Molecular Structure, 2018

A detailed structural analysis of two adamantane derivatives namely, ethyl 2-[(Z)-1-(adamantan-1-yl)-3-(phenyl)isothioureido]acetate I and ethyl 2-[(Z)-1-(adamantan-1-yl)-3-(4fluorophenyl)isothioureido]acetate II is carried out to understand the effect of fluorine substitution. The introduction of fluorine atom alters the crystal packing and is completely different from its parent compound. The fluorine substitution drastically reduced the intermolecular H•••H contacts and this reduction is compensated by intermolecular F•••H and F•••F contacts. The relative contributions of various intermolecular contacts present in these structures were quantified using Hirshfeld surface analysis. Energetically significant molecular pairs were identified from the crystal structures of these compounds using PIXEL method. The structures of I and II are optimized in gas and solvent phases using the B3LYP-D3/6-311++G(d,p) level of theory. The quantum theory of atoms-in-molecules (QTAIM) analysis was carried out to estimate the strengths of various intermolecular contacts present in these molecular dimers. The results suggest that the H-H bonding take part in the stabilization of crystal structures. The experimental and theoretical UV-Vis results show the variations in HOMO and LUMO energy levels. In silico docking analysis indicates that both compounds I M

Diamondoid Molecules with Applications in Biomedicine, Materials Science, Nanotechnology & Petroleum Science, 2012

INTRODUCTION Diamondoid molecules are cage-like, ultra stable and saturated hydrocar-bons. The basic repetitive unit of the diamondoids is a ten carbon tetracy-clic cage system called “adamantane” (Fig. 1.1). They are called “diamondoid” because they have at least one adamantane unit and their carbon–carbon framework is completely or largely superimposable on the diamond lattice (Balaban and Schleyer, 1978; Mansoori, 2007). The diamond lattices structure was first determined in 1913 by Bragg and Bragg using X-ray diffraction analysis (Bragg and Brag, 1913). Diamondoids show unique properties due to their exceptional atomic arrangements. Adamantane consists of cyclohexane rings in “chair” conformation. The name adamantane is derived from the Greek language word for diamond since its chemical structure is like the three-dimensional diamond subunit as it is shown in Fig. 1.2.

International Journal of Modern Physics C, 2006

We present tight binding molecular dynamics simulations of the diffusion and bonding of hydrogen in bulk diamond. The motion of hydrogen atoms and the resultant structural and electronic energy level changes are investigated. The hydrogen atoms were found to have a tendency to migrate to the surface layer of diamond, resulting in a local deformation of the lattice, creating new energy states above and below the Fermi energy in the bandgap of the diamond density of states. In the diamond bulk, at high hydrogen concentrations, vacancies created by a hydrogen atom are quickly filled with other hydrogen atoms causing a deformation of the diamond lattice, inducing H 2 formation. This creates new energy states above the Fermi energy and reduces the secondary bandgap of the diamond density of states.

Physical Review B, 2007

We compare fluctuation electron microscopy data to simulations from phenomenological atomic models and demonstrate a strong correspondence between some features in the experimental data and certain atomic configurations. This allows the nature of atomic clustering in a highly hydrogenated diamondlike carbon to be determined more closely. We compare the structural information garnered from fluctuation electron microscopy and Raman spectroscopy for a particular diamondlike carbon and find consistency between the two techniques in the region where their information overlaps.

Acta Physica Polonica A, 2019

Density functional theory, as implemented in SIESTA code, was utilized in this study to investigate the structural, electronic and stability properties of bare and hydrogenated small nanoclusters of diamond. The results obtained by studying different nanoparticles of diamond composed of 19, 50, and 104 carbon atoms, revealed that while the gap energy of hydrogenated nanodiamonds reduced from 8.2 to 6.5 eV by increasing the size of nanoparticles (number of carbon atoms), the bare nanodiamonds showed almost no gap energy except C19 sample which has the highest occupied molecular orbital-lowest unoccupied molecular orbital of about 0.33 eV. Electron affinity of hydrogenated samples was calculated and it was found that hydrogenated nanodiamond exhibits negative electron affinity. The quantum confinement effect found to be still significant for the sample larger than 1 nm i.e. the largest hydrogenated sample of C104H90 with a diameter of about 1.2 nm which showed greater gap energy in comparison to the bulk diamond. This achievement was explained considering electron affinity and partial density of states analysis. The calculated formation energy of the nanoparticles confirmed that the small hydrogenated nanoclusters of diamond have more stability compared to the bare nanodiamonds.

Journal of Chemical Sciences, 2012

In this investigation, a systematic attempt has been made to understand the interaction between adamantane and benzene using both ab initio and density functional theory methods. C-H...π type of interaction between C-H groups of adamantane and π cloud of benzene is found as the important attraction for complex formation. The study also reveals that the methylene (-CH 2) and methine (-CH) groups of adamantane interact with benzene resulting in different geometrical structures. And it is found that the former complex is stronger than the later. The diamondoid structure of adamantane enables it to interact with a maximum of four benzene molecules, each one along the four faces. The stability of the complex increases with increase in the number of benzene molecules. The energy decomposition analysis of adamantane-benzene complexes using DMA approach shows that the origin of the stability primarily arises from the dispersive interaction. The theory of atoms in molecules (AIM) supports the existence of weak interaction between the two systems. The electrostatic topography features provide clues for the mode of interaction of adamantane with benzene.