New modelling capability for nano-confined phase change materials

Lead Research Organisation: University of Cambridge
Department Name: Physics

Abstract

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Description We have developed new modelling capabilties to understand nanowires encapsulated within carbon nantubes. Our goal was to characterise these new materials and use these techniques to seach for phase transitions that could be used in phase-change memory. Our key finding so far are:

1. Helical-tellurium encapulsate nanowires including the predition of an electronic insulator-conducting transition.
2. Through first-principles modelling enhancemnt to electrical conductivity of carbon nanotubes using a nanowire filling.
3. Crystalline-Crystalline temperature induced structural phase transitions in encapsulated GeTe.
Exploitation Route * Developments in computer chips through carbon nanotube higher current interconnects.
* Nano-encapsulated phase change memory for electronic devices.
Sectors Digital/Communication/Information Technologies (including Software),Energy
 
Title Data for: Encapsulated nanowires : boosting electronic transport in carbon nanotubes 
Description The electrical conductivity of metallic carbon nanotubes (CNTs) quickly saturates with respect to bias voltage due to scattering from a large population of optical phonons. The decay of these dominant scatterers in pristine CNTs is too slow to offset an increased generation rate at high voltage bias. We demonstrate from first principles that encapsulation of one-dimensional atomic chains within a single-walled CNT can enhance the decay of "hot" phonons by providing additional channels for thermalization. Pacification of the phonon population growth reduces the electrical resistivity of metallic CNTs by 51% for an example system with encapsulated beryllium. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact 27downloads in 4 months 
URL http://wrap.warwick.ac.uk/id/eprint/93859
 
Title Research data supporting "Single-Atom Scale Structural Selectivity in Te Nanowires Encapsulated Inside Ultranarrow, Single-Walled Carbon Nanotubes" 
Description All information regarding this data has been included in the associated publication. The raw files are easily parsable using, e.g., Python. These files correspond to the theory part of the referred publication. Experiments were performed by our collaborators at the University of Warwick. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title Research data supporting 'Phase diagram of germanium telluride encapsulated in carbon nanotubes from first-principles searches' 
Description These data relate to low-energy structures identified as part of an ab initio structure search for germanium telluride nanowires encapsulated inside carbon nanotubes. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title Research data supporting 'Phase diagram of germanium telluride encapsulated in carbon nanotubes from first-principles searches' 
Description These data relate to low-energy structures identified as part of an ab initio structure search for germanium telluride nanowires encapsulated inside carbon nanotubes. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact Not yet 
URL https://doi.org/10.17863/CAM.11017
 
Title C2x: A tool for visualisation and input preparation for Castep and other electronic structure codes 
Description The c2x code fills two distinct roles. Its first role is in acting as a converter between the binary format .check files from the widely-used Castep [1] electronic structure code and various visualisation programs. Its second role is to manipulate and analyse the input and output files from a variety of electronic structure codes, including Castep, Onetep and Vasp, as well as the widely-used 'Gaussian cube' file format. Analysis includes symmetry analysis, and manipulation arbitrary cell transformations. It continues to be under development, with growing functionality, and is written in a form which would make it easy to extend it to working directly with files from other electronic structure codes. Data which c2x is capable of extracting from Castep's binary checkpoint files include charge densities, spin densities, wavefunctions, relaxed atomic positions, forces, the Fermi level, the total energy, and symmetry operations. It can recreate .cell input files from checkpoint files. Volumetric data can be output in formats useable by many common visualisation programs, and c2x will itself calculate integrals, expand data into supercells, and interpolate data via combinations of Fourier and trilinear interpolation. It can extract data along arbitrary lines (such as lines between atoms) as 1D output. C2x is able to convert between several common formats for describing molecules and crystals, including the .cell format of Castep. It can construct supercells, reduce cells to their primitive form, and add specified -point meshes. It uses the spglib library [2] to report symmetry information, which it can add to .cell files. C2x is a command-line utility, so is readily included in scripts. It is available under the GPL and can be obtained from http://www.c2x.org.uk. It is believed to be the only open-source code which can read Castep's .check files, so it will have utility in other projects. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2017 
Impact Non yet. It is believed to be the only open-source code which can read Castep's .check files, so it will have utility in other projects. 
URL http://dx.doi.org/10.17632/wj5hcj7x39.1