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Papers by Elias Mahmoudinezhad Zirdehi

Research paper thumbnail of Long-range strain correlations in 3D quiescent glass forming liquids

EPL (Europhysics Letters)

PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids ... more PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids PACS 62.20.Fe-Deformation and plasticity (including yield, ductility, and superplasticity) Abstract.-We present a quantitative study of strain correlations in quiescent supercooled liquids and glasses. Recent two-dimensional computer simulations and experiments indicate that even supercooled liquids exhibit long-lived, long-range strain correlations. Here we investigate this issue in three dimensions via experiments on hard sphere colloids and molecular dynamics simulations of a glass forming binary Lennard Jones mixture. Both in the glassy state and in the supercooled regime, strain correlations are found to decay with a 1/r 3 power-law behavior, reminiscent of elastic fields around an inclusion. Moreover, theoretical predictions on the time dependence of the correlation amplitude are in line with the results obtained from experiments and simulations. It is argued that the size of the domain, which exhibits a cooperative strain pattern in a supercooled liquid, is determined by the product of the speed of sound with the structural relaxation time. While this length is of the order of nanometers in the normal liquid state, it grows to macroscale when approaching the glass transition.

Research paper thumbnail of A comprehensive study on the encapsulation of methane in single-walled carbon nanotubes

This paper aims at exploring the characteristics of a single methane molecule encapsulated in sem... more This paper aims at exploring the characteristics of a single methane molecule encapsulated in semi-infinite single-walled carbon nanotubes. On the basis of Lennard-Jones potential function along with the continuum approximation and applied mathematics, single integrals are presented to formulate the van der Waals interaction energy and suction energy between a single methane molecule and a carbon nanotube. The preferred position and orientation of methane with regard to the nanotube axis has been fully investigated for different nanotube radii. To this end, it is assumed that the whole molecule rotates in all directions inside the nanotube. It is found that for certain radii of nanotubes in which the suction energy imparted to methane is negative, the whole methane molecule is symmetric with respect to the tube axis when it is inside the carbon nanotube. But, when the suction energy has positive values, as the tube radius increases the methane molecule gets closer to the wall of nanotube and finally locates near its wall in the form of a downward tripod. Furthermore, the optimum nanotube radius which gives rise to maximum suction energy has been calculated. The results obtained in this study can be conducted as means of further investigations for methane storage in carbon nanotubes.

Research paper thumbnail of An accurate spring-mass finite element model for vibration analysis of single-walled carbon nanotubes

An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for investigating the vibrational characteristics of single-walled carbon nanotubes (SWCNTs). Atoms are replaced by lumped mass elements at their locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the interatomic interactions. The effect of out of plane angle variation energy is incorporated into the model. The obtained results for the fundamental frequency of single-walled carbon nanotubes of various kinds are graphically illustrated. The influences of some commonly-used boundary conditions and changes in the nanotube geometrical parameters on vibration frequencies are examined. The numerical results show good agreement with other published results in the literature. Also, some novel relations are deduced which can be more useful in predicting the fundamental frequency of SWCNTs with great number of atoms.

Research paper thumbnail of An accurate spring-mass model for predicting mechanical properties of single-walled carbon nanotubes

An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for estimating Young's and shear modulus of single-walled carbon nanotubes (SWCNTs). Lumped mass elements are placed at the atom locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the inter-atomic interactions.

Research paper thumbnail of Vibration analysis of circular and square single-layered graphene sheets: An accurate spring mass model

The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) ... more The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) are investigated by developing a finite element formulation based on an accurate spring mass model. According to the present atomistic structural model, nodes are defined at the atom locations and suitable three-dimensional spring-type elements are employed to connect these nodes which are representing interatomic interactions.

Research paper thumbnail of Different motion patterns of triple-walled carbon nanotube oscillators

Journal of Vibration and …, 2012

Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted ... more Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted much attention in recent years. A number of studies on double-walled carbon nanotube (DWCNT) oscillators can be found in the literature, while other mechanisms of these oscillators with a higher number of oscillating nanotubes have not been well studied. This paper aims to investigate the motion properties of triple-walled carbon nanotube (TWCNT) oscillators in which the inner and middle tubes have telescopic motions with respect to the outer tube. To this end, the continuum approximation together with the Lennard-Jones potential function is utilized. In comparison with DWCNT oscillators, the triple-walled ones have shown a variety of motion patterns. In this respect, different types of motion patterns are classified and demonstrated. Moreover, it is observed that these nano-oscillators are so sensitive to their initial conditions. For this reason, a phase division of initial separation distances that generate different motion patterns is also presented.

Research paper thumbnail of Preferred Position and Orientation of Anticancer Drug Cisplatin During Encapsulation Into Single-Walled Carbon Nanotubes

… of Nanotechnology in …, 2012

Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of can... more Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of cancers. However, this anticancer drug has a number of side effects such as kidney and nerve damages, anaphylactic reactions, hearing loss, nausea, and vomiting that strongly restrict its function. In the present study, single-walled carbon nanotubes (SWCNTs) are used as protective drug carriers which can decrease these severe side effects to some extent. Using the hybrid discrete-continuum model in conjunction with Lennard-Jones ...

Research paper thumbnail of On the van der Waals interaction of carbon nanocones

Journal of Physics and …, 2012

Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and e... more Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and eccentric carbon nanocones with different or identical sizes are investigated in this paper. Also, on the basis of classical mathematical modeling techniques, a new semi-analytical solution is given to evaluate the van der Waals potential energy and interaction force distributions of two concentric carbon nanocones. Finally, a universal potential energy is presented for the carbon nanocones.

Research paper thumbnail of Long-range strain correlations in 3D quiescent glass forming liquids

EPL (Europhysics Letters)

PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids ... more PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids PACS 62.20.Fe-Deformation and plasticity (including yield, ductility, and superplasticity) Abstract.-We present a quantitative study of strain correlations in quiescent supercooled liquids and glasses. Recent two-dimensional computer simulations and experiments indicate that even supercooled liquids exhibit long-lived, long-range strain correlations. Here we investigate this issue in three dimensions via experiments on hard sphere colloids and molecular dynamics simulations of a glass forming binary Lennard Jones mixture. Both in the glassy state and in the supercooled regime, strain correlations are found to decay with a 1/r 3 power-law behavior, reminiscent of elastic fields around an inclusion. Moreover, theoretical predictions on the time dependence of the correlation amplitude are in line with the results obtained from experiments and simulations. It is argued that the size of the domain, which exhibits a cooperative strain pattern in a supercooled liquid, is determined by the product of the speed of sound with the structural relaxation time. While this length is of the order of nanometers in the normal liquid state, it grows to macroscale when approaching the glass transition.

Research paper thumbnail of A comprehensive study on the encapsulation of methane in single-walled carbon nanotubes

This paper aims at exploring the characteristics of a single methane molecule encapsulated in sem... more This paper aims at exploring the characteristics of a single methane molecule encapsulated in semi-infinite single-walled carbon nanotubes. On the basis of Lennard-Jones potential function along with the continuum approximation and applied mathematics, single integrals are presented to formulate the van der Waals interaction energy and suction energy between a single methane molecule and a carbon nanotube. The preferred position and orientation of methane with regard to the nanotube axis has been fully investigated for different nanotube radii. To this end, it is assumed that the whole molecule rotates in all directions inside the nanotube. It is found that for certain radii of nanotubes in which the suction energy imparted to methane is negative, the whole methane molecule is symmetric with respect to the tube axis when it is inside the carbon nanotube. But, when the suction energy has positive values, as the tube radius increases the methane molecule gets closer to the wall of nanotube and finally locates near its wall in the form of a downward tripod. Furthermore, the optimum nanotube radius which gives rise to maximum suction energy has been calculated. The results obtained in this study can be conducted as means of further investigations for methane storage in carbon nanotubes.

Research paper thumbnail of An accurate spring-mass finite element model for vibration analysis of single-walled carbon nanotubes

An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for investigating the vibrational characteristics of single-walled carbon nanotubes (SWCNTs). Atoms are replaced by lumped mass elements at their locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the interatomic interactions. The effect of out of plane angle variation energy is incorporated into the model. The obtained results for the fundamental frequency of single-walled carbon nanotubes of various kinds are graphically illustrated. The influences of some commonly-used boundary conditions and changes in the nanotube geometrical parameters on vibration frequencies are examined. The numerical results show good agreement with other published results in the literature. Also, some novel relations are deduced which can be more useful in predicting the fundamental frequency of SWCNTs with great number of atoms.

Research paper thumbnail of An accurate spring-mass model for predicting mechanical properties of single-walled carbon nanotubes

An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for estimating Young's and shear modulus of single-walled carbon nanotubes (SWCNTs). Lumped mass elements are placed at the atom locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the inter-atomic interactions.

Research paper thumbnail of Vibration analysis of circular and square single-layered graphene sheets: An accurate spring mass model

The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) ... more The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) are investigated by developing a finite element formulation based on an accurate spring mass model. According to the present atomistic structural model, nodes are defined at the atom locations and suitable three-dimensional spring-type elements are employed to connect these nodes which are representing interatomic interactions.

Research paper thumbnail of Different motion patterns of triple-walled carbon nanotube oscillators

Journal of Vibration and …, 2012

Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted ... more Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted much attention in recent years. A number of studies on double-walled carbon nanotube (DWCNT) oscillators can be found in the literature, while other mechanisms of these oscillators with a higher number of oscillating nanotubes have not been well studied. This paper aims to investigate the motion properties of triple-walled carbon nanotube (TWCNT) oscillators in which the inner and middle tubes have telescopic motions with respect to the outer tube. To this end, the continuum approximation together with the Lennard-Jones potential function is utilized. In comparison with DWCNT oscillators, the triple-walled ones have shown a variety of motion patterns. In this respect, different types of motion patterns are classified and demonstrated. Moreover, it is observed that these nano-oscillators are so sensitive to their initial conditions. For this reason, a phase division of initial separation distances that generate different motion patterns is also presented.

Research paper thumbnail of Preferred Position and Orientation of Anticancer Drug Cisplatin During Encapsulation Into Single-Walled Carbon Nanotubes

… of Nanotechnology in …, 2012

Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of can... more Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of cancers. However, this anticancer drug has a number of side effects such as kidney and nerve damages, anaphylactic reactions, hearing loss, nausea, and vomiting that strongly restrict its function. In the present study, single-walled carbon nanotubes (SWCNTs) are used as protective drug carriers which can decrease these severe side effects to some extent. Using the hybrid discrete-continuum model in conjunction with Lennard-Jones ...

Research paper thumbnail of On the van der Waals interaction of carbon nanocones

Journal of Physics and …, 2012

Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and e... more Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and eccentric carbon nanocones with different or identical sizes are investigated in this paper. Also, on the basis of classical mathematical modeling techniques, a new semi-analytical solution is given to evaluate the van der Waals potential energy and interaction force distributions of two concentric carbon nanocones. Finally, a universal potential energy is presented for the carbon nanocones.