Investigating fullerene-oxide nanostructure as an adsorbent of ammonia: Complexation efficiency by density functional theory

A model of OC20 fullerene-oxide (FO) was investigated in this work for adsorbing the ammonia (NH3) substance by the hypothesis of formations of bimolecular complexes of the two substances. To affirm such hypothesis, the models of singular NH3 and FO were optimized to reach the minimized energy structures and all possibilities of their interactions configurations were examined. As a consequence, three NH3@FO bimolecular complex models were obtained for reaching the point of complex formations. Details of interactions indicated both direct and indirect contributions of the oxidized region of FO to interactions with both H and N atomic sites of NH3. In this regard, CPLX3 with two types of H. . . O and N. . . C interactions was seen to be at the highest strength of adsorption and complex formation in comparison with CPLX1 and CPLX2 models including only one interaction of each of H. . . O and N. . . C type, respectively. Moreover, the obtained electronic molecular orbital features revealed the sensor function of FO material versus the NH3 substance. As a consequence, the hypothesis of NH3@FO complexes formation was affirmed with two proposed functions of removal and detection for the investigated FO material. All results of this work were obtained by details through performing density functional theory (DFT) calculations.

Structural and electronic properties of C60 fullerene network self-assembled on metal-covered semiconductor surfaces

Using first-principles density functional theory calculations, we made an accurate structural characterization of the C₆₀ superstructures self-assembled on the Tl-adsorbed Si(111) and Ge(111) surfaces, which finds a good agreement with the recent scanning tunneling microscopy observations. Our band structure calculations revealed the semi-metallic character of the C₆₀/Tl/Si(111) system, while the C₆₀/Tl/Ge(111) system was found to show up the pronounced metallic character due to the cascade of the flat bands lying in the vicinity of the Fermi level. The latter is a fingerprint for strong correlation effects in the C₆₀/Tl/Ge(111) system, which makes it a promising object for studying electrical transport phenomena and opens the prospects for its application in the molecular-based electronic devices. We elucidated the details of the molecule-substrate and intermolecular interactions and discussed the character of a charge transfer in both systems.

Bonding network and stability of clusters: the case study of Al13TM4 pseudo-tenfold surfaces

Clusters, i.e. polyhedral geometric entities, are widely used to describe the structure of complex intermetallic compounds. However, little is generally known about their physical significance. The atomic and electronic structures of the Al13TM4 complex intermetallic compounds (TM = Fe, Co, Ru, Rh) have been investigated using a wide range of ab initio tools in order to examine the influence of the chemical composition on the pertinence of the bulk structure description based on 3D clusters. In addition, since surface studies were found to be a relevant approach to address the question of cluster stability in complex phases, the interplay of the cluster substructure with the 2D surface is addressed in the case of the Al13Co4(100) and Al13Fe4(010) surfaces.

Rotational switches in the two-dimensional fullerene quasicrystal

One of the essential components of molecular electronic circuits are switching elements that are stable in two different states and can ideally be switched on and off many times. Here, distinct buckminsterfullerenes within a self-assembled monolayer, forming a two-dimensional dodecagonal quasicrystal on a Pt-terminated Pt3Ti(111) surface, are identified to form well separated molecular rotational switching elements. Employing scanning tunneling microscopy, the molecular-orbital appearance of the fullerenes in the quasicrystalline monolayer is resolved. Thus, fullerenes adsorbed on the 36 vertex configuration are identified to exhibit a distinctly increased mobility. In addition, this finding is verified by differential conductance measurements. The rotation of these mobile fullerenes can be triggered frequently by applied voltage pulses, while keeping the neighboring molecules immobile. An extensive analysis reveals that crystallographic and energetic constraints at the molecule/metal interface induce an inequality of the local potentials for the 36 and 32.4.3.4 vertex sites and this accounts for the switching ability of fullerenes on the 36 vertex sites. Consequently, a local area of the 8/3 approximant in the two-dimensional fullerene quasicrystal consists of single rotational switching fullerenes embedded in a matrix of inert molecules. Furthermore, it is deduced that optimization of the intermolecular interactions between neighboring fullerenes hinders the realization of translational periodicity in the fullerene monolayer on the Pt-terminated Pt3Ti(111) surface.