A modelling algorithm for amorphous covalent triazine-based polymers.

Rational and purposeful designs of amorphous materials with desirable structures are difficult to implement due to the complex and unordered nature of such materials. In this work, a modelling algorithm was proposed for amorphous covalent triazine-based polymers to construct atomistic representative models that can reproduce the experimentally measured properties of experimental samples. The constructed models were examined through comparisons of simulated and experimental properties, such as surface area, pore volume, and structure factor, and further validated by the good consistency observed among these properties. To assess the predictive capability of the modelling algorithm, we used a new covalent triazine-based polymer and predicted its porosity by constructing a simulated model. The predicted results on the surface area and pore volume of the simulated model were quantitatively consistent with the experimental data derived from the experimentally synthesized sample. This consistency reveals the predictive capacity of the proposed modelling algorithm. The algorithm could be a promising approach to predict and develop advanced covalent triazine-based polymers for multiple applications.

Density Functional Theory Calculations of the Quantum Capacitance of Graphene Oxide as a Supercapacitor Electrode.

Graphene oxide has become an attractive electrode-material candidate for supercapacitors thanks to its higher specific capacitance compared to graphene. The quantum capacitance makes relative contributions to the specific capacitance, which is considered as the major limitation of graphene electrodes, while the quantum capacitance of graphene oxide is rarely concerned. This study explores the quantum capacitance of graphene oxide, which bears epoxy and hydroxyl groups on its basal plane, by employing density functional theory (DFT) calculations. The results demonstrate that the total density of states near the Fermi level is significantly enhanced by introducing oxygen-containing groups, which is beneficial for the improvement of the quantum capacitance. Moreover, the quantum capacitances of the graphene oxide with different concentrations of these two oxygen-containing groups are compared, revealing that more epoxy and hydroxyl groups result in a higher quantum capacitance. Notably, the hydroxyl concentration has a considerable effect on the capacitive behavior.

Atomistic structure generation of covalent triazine-based polymers by molecular simulation.

The structures of amorphous materials are generally difficult to characterize and comprehend due to their unordered nature and indirect measurement techniques. However, molecular simulation has been considered as an alternative method that can provide molecular-level information supplementary to experimental techniques. In this work, a new approach for modelling the atomistic structures of amorphous covalent triazine-based polymers is proposed and employed on two experimentally synthesized covalent triazine-based polymers. To examine the proposed modelling approach, the properties of the established models, such as surface areas, pore volumes, structure factors and N2 adsorption isotherms, were calculated and compared with the experimental data. Excellent consistencies were observed between the simulated models and experimental samples, consequently validating the proposed models and the modelling approach. Moreover, the proposed modelling approach can be applied to new covalent triazine-based polymers for predictive purposes and to provide design strategies for future synthesis works.

A versatile rotary-stage high frequency probe station for studying magnetic films and devices.

We present a rotary-stage microwave probe station suitable for magnetic films and spintronic devices. Two stages, one for field rotation from parallel to perpendicular to the sample plane (out-of-plane) and the other intended for field rotation within the sample plane (in-plane) have been designed. The sample probes and micro-positioners are rotated simultaneously with the stages, which allows the field orientation to cover θ from 0(∘) to 90(∘) and φ from 0(∘) to 360(∘). θ and φ being the angle between the direction of current flow and field in a out-of-plane and an in-plane rotation, respectively. The operation frequency is up to 40 GHz and the magnetic field up to 1 T. The sample holder vision system and probe assembly are compactly designed for the probes to land on a wafer with diameter up to 3 cm. Using homemade multi-pin probes and commercially available high frequency probes, several applications including 4-probe DC measurements, the determination of domain wall velocity, and spin transfer torque ferromagnetic resonance are demonstrated.