The sphere-in-contact model of carbon materials

Abstract

A sphere-in-contact model is presented that is used to build physical models of carbon materials such as graphite, graphene, carbon nanotubes and fullerene. Unlike other molecular models, these models have correct scale and proportions because the carbon atoms are represented by their atomic radius, in contrast to the more commonly used space-fill models, where carbon atoms are represented by their van der Waals radii. Based on a survey taken among 65 undergraduate chemistry students and 28 PhD/postdoctoral students with a background in molecular modeling, we found misconceptions arising from incorrect visualization of the size and location of the electron density located in carbon materials. Based on analysis of the survey and on a conceptual basis we show that the sphere-in-contact model provides an improved molecular representation of the electron density of carbon materials compared to other molecular models commonly used in science textbooks (i.e., wire-frame, ball-and-stick, space-fill). We therefore suggest that its use in chemistry textbooks along with the ball-and-stick model would significantly enhance the visualization of molecular structures according to their electron density.Graphical AbstractA sphere-in-contact model of C60-fullereneElectronic supplementary materialThe online version of this article (doi:10.1007/s00894-015-2895-7) contains supplementary material, which is available to authorized users.

DFT-D3 study of H2 and N2 chemisorption over cobalt promoted Ta3N5-(100), (010) and (001) surfaces

“…20 Based on the sphere-incontact model this result suggests the formation of covalent bonds between nitrogen and cobalt. 21 However, the electronic structure of Ta 3 N 5 does not have any unpaired electrons on the surface nitrogen, which indicates when cobalt is co-adsorbed, these sites are re-hybridized into states with unpaired electrons, that can then form the covalent Co-N.…”

DFT-D3 Study of Molecular N2 and H2 Activation on Co3Mo3N Surfaces

“…In the following section, we provide evidence that there are two bonding interactions that take place based on the sphere-in-contact model. 65 We have taken literature values for the atomic radius of the elements participating in the bonding and drawn to scale a sphere-in-contact model of the tilt end-on adsorption configuration for N 2 on Co 3 Mo 3 N. This is depicted in Figure 5 From the optimized structures presented in Table 2, we find that the tilt angle ranges between 152 and 158°with an average value at 155°. We have used the sphere-in-contact model to provide an explanation of the bonding in the tilt end-on configuration.…”

“…This is a well-defined adsorption configuration with a tilt angle equal to 155° in which the dihedral d (Co–Mo–N–N) of this bond is found to be 0. In the following section, we provide evidence that there are two bonding interactions that take place based on the sphere-in-contact model . We have taken literature values for the atomic radius of the elements participating in the bonding and drawn to scale a sphere-in-contact model of the tilt end-on adsorption configuration for N 2 on Co 3 Mo 3 N. This is depicted in Figure…”

Study of a rhombohedral graphite X-ray filter using the sphere-in-contact model

“…In the sphere-in-contact model [28], the bond length (BL) between atoms is the sum of their atomic radii (AR):…”

“…We have recently shown that there is one more physical molecular model, the sphere-in-contact model. [26] This new model is intermediate between the wire-frame and space-fill models and has the basic advantage that it shows the location of the electron density more accurately. In this paper, we use the sphere-in-contact model design to build the structure of rhombohedral graphite and pinpoint new properties with potential applications through theoretical treatment of the spherein-contact model.…”