Synthesis and Characterization of Covalent Organic Polymer (COP-1) Adsorbent for Carbon Dioxide Capture

Carbon dioxide (CO2) capture from natural gas at high pressure conditions with high CO2 capture ability as well as high selectivity of CO2 over CH4 at low cost remains a major challenge. Recently, covalent organic polymer (COP-1), an adsorbent discovered by Patel (2012) reports the highest carbon dioxide capture of all time of 5616 mg g-1 at 200 bar with high thermal stability and desirable characteristics promising for natural gas application. However, the current research information on COP-1 is limited where Patel (2012) only concentrates on CO2 / N2 separation and there is no data on CH4 adsorption which remains a research gap. Besides, the synthesis methodology is not described in detail hence posing a major challenge to replicate the synthesis of COP-1 for further studies. The objective of this research is to synthesis and characterise COP-1 to validate the material synthesised and study on morphology of COP-1 as well as CO2 / CH4 adsorption capacity. COP-1 synthesised in this research are characterised using analysis of FT-IR, XRD, NMR, CHN, EDX, TGA, BET surface area, pore size, and FESEM. Pure gas adsorption of CO2 and CH4 has also been performed using BELSORP. Overall, the characterisation result shows similarities to Patel (2012) in terms of linkage, functional group and absence of crystallinity with difference such that both surface area and CO2 capture using COP-1 in this research is about half of that obtained by Patel (2012). Pure gas adsorption of CO2 and CH4 using COP-1 in this research is found to be 0.59244 mmol g-1 and 0.11405 mmol g-1 respectively. A simple selectivity of CO2 / CH4 is calculated as 5.19. This research closed the research gap for CH4 capture at low pressure as well as morphology of COP-1. Further study could be done on CO2 / CH4 binary gas selectivity with high amount of CO2 at high pressure similar to natural gas application

Geometric phases in discrete dynamical systems

In order to study the behaviour of discrete dynamical systems under adiabatic cyclic variations of their parameters, we consider discrete versions of adiabatically-rotated rotators. Paralleling the studies in continuous systems, we generalize the concept of geometric phase to discrete dynamics and investigate its presence in these rotators. For the rotated sine circle map, we demonstrate an analytical relationship between the geometric phase and the rotation number of the system. For the discrete version of the rotated rotator considered by Berry, the rotated standard map, we further explore this connection as well as the role of the geometric phase at the onset of chaos. Further into the chaotic regime, we show that the geometric phase is also related to the diffusive behaviour of the dynamical variables and the Lyapunov exponent

Synthesis and Characterization of Covalent Organic Polymer (COP-1) Adsorbent for Carbon Dioxide Capture

Carbon dioxide (CO2) capture from natural gas at high pressure conditions with high CO2 capture ability as well as high selectivity of CO2 over CH4 at low cost remains a major challenge. Recently, covalent organic polymer (COP-1), an adsorbent discovered by Patel (2012) reports the highest carbon dioxide capture of all time of 5616 mg g-1 at 200 bar with high thermal stability and desirable characteristics promising for natural gas application. However, the current research information on COP-1 is limited where Patel (2012) only concentrates on CO2 / N2 separation and there is no data on CH4 adsorption which remains a research gap. Besides, the synthesis methodology is not described in detail hence posing a major challenge to replicate the synthesis of COP-1 for further studies. The objective of this research is to synthesis and characterise COP-1 to validate the material synthesised and study on morphology of COP-1 as well as CO2 / CH4 adsorption capacity. COP-1 synthesised in this research are characterised using analysis of FT-IR, XRD, NMR, CHN, EDX, TGA, BET surface area, pore size, and FESEM. Pure gas adsorption of CO2 and CH4 has also been performed using BELSORP. Overall, the characterisation result shows similarities to Patel (2012) in terms of linkage, functional group and absence of crystallinity with difference such that both surface area and CO2 capture using COP-1 in this research is about half of that obtained by Patel (2012). Pure gas adsorption of CO2 and CH4 using COP-1 in this research is found to be 0.59244 mmol g-1 and 0.11405 mmol g-1 respectively. A simple selectivity of CO2 / CH4 is calculated as 5.19. This research closed the research gap for CH4 capture at low pressure as well as morphology of COP-1. Further study could be done on CO2 / CH4 binary gas selectivity with high amount of CO2 at high pressure similar to natural gas application

Strain-Dependence of Surface Diffusion: Ag on Ag(111) and Pt(111)

Using density-functional theory with the local-density approximation and the generalized gradient approximation we compute the energy barriers for surface diffusion for Ag on Pt(111), Ag on one monolayer of Ag on Pt(111), and Ag on Ag(111). The diffusion barrier for Ag on Ag(111) is found to increase linearly with increasing lattice constant. We also discuss the reconstruction that has been found experimentally when two Ag layers are deposited on Pt(111). Our calculations explain why this strain driven reconstruction occurs only after two Ag layers have been deposited.Comment: 4 pages, 3 figures, Phys. Rev. B 55 (1997), in pres

Anisotropy of Growth of the Close-Packed Surfaces of Silver

The growth morphology of clean silver exhibits a profound anisotropy: The growing surface of Ag(111) is typically very rough while that of Ag(100) is smooth and flat. This serious and important difference is unexpected, not understood, and hitherto not observed for any other metal. Using density functional theory calculations of self-diffusion on flat and stepped Ag(100) we find, for example, that at flat regions a hopping mechanism is favored, while across step edges diffusion proceeds by an exchange process. The calculated microscopic parameters explain the experimentally reported growth properties.Comment: RevTeX, 4 pages, 3 figures in uufiles form, to appear in Phys. Rev. Let

The long-wavelength behaviour of the exchange-correlation kernel in the Kohn-Sham theory of periodic systems

The polarization-dependence of the exchange-correlation (XC) energy functional of periodic insulators within Kohn-Sham (KS) density-functional theory requires a ${\cal O} (1/q^2)$ divergence in the XC kernel for small vectors q. This behaviour, exemplified for a one-dimensional model semiconductor, is also observed when an insulator happens to be described as a KS metal, or vice-versa. Although it can occur in the exchange-only kernel, it is not found in the usual local, semi-local or even non-local approximations to KS theory. We also show that the test-charge and electronic definitions of the macroscopic dielectric constant differ from one another in exact KS theory, but are equivalent in the above-mentioned approximations

Theoretical study of O adlayers on Ru(0001)

Recent experiments performed at high pressures indicate that ruthenium can support unusually high concentrations of oxygen at the surface. To investigate the structure and stability of high coverage oxygen structures, we performed density functional theory calculations, within the generalized gradient approximation, for O adlayers on Ru(0001) from low coverage up to a full monolayer. We achieve quantitative agreement with previous low energy electron diffraction intensity analyses for the (2x2) and (2x1) phases and predict that an O adlayer with a (1x1) periodicity and coverage of 1 monolayer can form on Ru(0001), where the O adatoms occupy hcp-hollow sites.Comment: RevTeX, 6 pages, 4 figure

Lattice Dynamics and the High Pressure Equation of State of Au

Elastic constants and zone-boundary phonon frequencies of gold are calculated by total energy electronic structure methods to twofold compression. A generalized force constant model is used to interpolate throughout the Brillouin zone and evaluate moments of the phonon distribution. The moments are used to calculate the volume dependence of the Gruneisen parameter in the fcc solid. Using these results with ultrasonic and shock data, we formulate the complete free energy for solid Au. This free energy is given as a set of closed form expressions, which are valid to compressions of at least V/V_0 = 0.65 and temperatures up to melting. Beyond this density, the Hugoniot enters the solid-liquid mixed phase region. Effects of shock melting on the Hugoniot are discussed within an approximate model. We compare with proposed standards for the equation of state to pressures of ~200 GPa. Our result for the room temperature isotherm is in very good agreement with an earlier standard of Heinz and Jeanloz.Comment: 13 pages, 8 figures. Accepted by Phys. Rev.

Surface relaxation and ferromagnetism of Rh(001)

The significant discrepancy between first-principles calculations and experimental analyses for the relaxation of the (001) surface of rhodium has been a puzzle for some years. In this paper we present density functional theory calculations using the local-density approximation and the generalized gradient approximation of the exchange-correlation functional. We investigate the thermal expansion of the surface and the possibility of surface magnetism. The results throw light on several, hitherto overlooked, aspects of metal surfaces. We find, that, when the free energy is considered, density-functional theory provides results in good agreement with experiments.Comment: 6 pages, 4 figures, submitted to Phys. Rev. Lett. (April 28, 1996

Ab initio pseudopotentials for electronic structure calculations of poly-atomic systems using density-functional theory

The package fhi98PP allows one to generate norm-conserving pseudopotentials adapted to density-functional theory total-energy calculations for a multitude of elements throughout the periodic table, including first-row and transition metal elements. The package also facilitates a first assessment of the pseudopotentials' transferability, either in semilocal or fully separable form, by means of simple tests carried out for the free atom. Various parameterizations of the local-density approximation and the generalized gradient approximation for exchange and correlation are implemented.Comment: 44 pages, 5 Postscript figures, epsfig, elsart, psfrag, submitted to Comput. Phys. Commun. Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm