E-Thesis 301 views 86 downloads
Molecular dynamics simulations of nanoclusters in neuromorphic systems / WENKAI WU
Swansea University Author: WENKAI WU
DOI (Published version): 10.23889/SUthesis.63613
Abstract
Neuromorphic computing is a new computing paradigm that deals with computing tasks using inter-connected artificial neurons inspired by the natural neurons in the human brain. This computational architecture is more efficient in performing many complex tasks such a pattern recognition and has promis...
| Published: |
Swansea, Wales, UK
2023
|
|---|---|
| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Palmer, Richard E. and Pavloudis, Theodoros. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa63613 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| first_indexed |
2023-06-08T14:47:13Z |
|---|---|
| last_indexed |
2023-06-08T14:47:13Z |
| id |
cronfa63613 |
| recordtype |
RisThesis |
| fullrecord |
<?xml version="1.0" encoding="utf-8"?><rfc1807 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><bib-version>v2</bib-version><id>63613</id><entry>2023-06-08</entry><title>Molecular dynamics simulations of nanoclusters in neuromorphic systems</title><swanseaauthors><author><sid>74bbf8e3606de3fcf398fc6151976b46</sid><firstname>WENKAI</firstname><surname>WU</surname><name>WENKAI WU</name><active>true</active><ethesisStudent>false</ethesisStudent></author></swanseaauthors><date>2023-06-08</date><abstract>Neuromorphic computing is a new computing paradigm that deals with computing tasks using inter-connected artificial neurons inspired by the natural neurons in the human brain. This computational architecture is more efficient in performing many complex tasks such a pattern recognition and has promise at overcoming some of the limitations of conventional computers. Among the emerging types of artificial neurons, a cluster-based neuromorphic device is a promising system with good costefficiency because of a simple fabrication process. This device functions using the formation and breakage of the connections (“synapses”) between clusters, driven by the bias voltage applied to the clusters. The mechanisms of the formation and breakage of these connections are thus of the utmost interest. In this thesis, the molecular dynamics simulation method is used to explore the mechanisms of the formation and breakage of the connections (“filaments”) between the clusters in a model of neuromorphic device. First, the Joule heating mechanism of filament breakage is explored using a model consisting of Au nanowire that connects two Au1415 clusters. Upon heating, the atoms of the nanofilament gradually aggregate towards the clusters, causing the middle of the wire to graduallythin and then suddenly break. Most of the system remains crystalline during this process, but the centre becomes molten. The terminal clusters increase the melting point of the nanowires by fixing them and act as recrystallisation regions. A strong dependence of the breaking temperature is found not only on the width of the nanowires but also their length and atomic structure. Secondly, the bridge formation and thermal breaking processes between Au1415 clusters on a graphite substrate are also simulated. The bridging process , which can heal a broken filament, is driven by diffusion of gold along the graphite substrate. The characteristic times of bridge formation are explored at elevated simulation temperatures to estimate the longer characteristic times of formation at room-temperature conditions. The width of the bridge formed has a power-law dependence on the simulation time, and the mechanism is a combination of diffusion and viscous flow. Simulations of bridgebreaking are also conducted and reveal the existence of a voltage threshold that must be reached to activate the breakage. The role of the substrate in the bridge formation and breakage processes is revealed as a medium of diffusion. Lastly, to explore future potential cluster materials, the thermal behaviour of Pb-Al core-shell clusters is studied. The core and shell are found to melt separately. In fact, the core atoms of nanoclusters tend to escape their shells and partially cover them, leading to a preference for a segregated state. The melting point of the core can either be depressed or elevated, depending on the thickness of the shell due to different mechanisms.</abstract><type>E-Thesis</type><journal/><volume/><journalNumber/><paginationStart/><paginationEnd/><publisher/><placeOfPublication>Swansea, Wales, UK</placeOfPublication><isbnPrint/><isbnElectronic/><issnPrint/><issnElectronic/><keywords>Neuromorphic Computing, Cluster-Based Neuromorphic Devices, Molecular Dynamics Simulation, Filament Formation and Breakage, Joule Heating Mechanism, Nanocluster, Nanowire, Diffusion, Melting</keywords><publishedDay>24</publishedDay><publishedMonth>5</publishedMonth><publishedYear>2023</publishedYear><publishedDate>2023-05-24</publishedDate><doi>10.23889/SUthesis.63613</doi><url/><notes/><college>COLLEGE NANME</college><CollegeCode>COLLEGE CODE</CollegeCode><institution>Swansea University</institution><supervisor>Palmer, Richard E. and Pavloudis, Theodoros.</supervisor><degreelevel>Doctoral</degreelevel><degreename>Ph.D</degreename><degreesponsorsfunders>Faculty of Science and Engineering, Swansea University</degreesponsorsfunders><apcterm/><funders/><projectreference/><lastEdited>2023-09-29T10:31:52.7756477</lastEdited><Created>2023-06-08T15:40:49.9014570</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering</level></path><authors><author><firstname>WENKAI</firstname><surname>WU</surname><order>1</order></author></authors><documents><document><filename>63613__27772__f0c5ea88ac354c9f9271cda21020149b.pdf</filename><originalFilename>2023_Wu_W.final.63613.pdf</originalFilename><uploaded>2023-06-08T15:49:09.6064878</uploaded><type>Output</type><contentLength>65654775</contentLength><contentType>application/pdf</contentType><version>E-Thesis – open access</version><cronfaStatus>true</cronfaStatus><documentNotes>Copyright: The Author, Wenkai Wu, 2023.</documentNotes><copyrightCorrect>true</copyrightCorrect><language>eng</language></document></documents><OutputDurs/></rfc1807> |
| spelling |
v2 63613 2023-06-08 Molecular dynamics simulations of nanoclusters in neuromorphic systems 74bbf8e3606de3fcf398fc6151976b46 WENKAI WU WENKAI WU true false 2023-06-08 Neuromorphic computing is a new computing paradigm that deals with computing tasks using inter-connected artificial neurons inspired by the natural neurons in the human brain. This computational architecture is more efficient in performing many complex tasks such a pattern recognition and has promise at overcoming some of the limitations of conventional computers. Among the emerging types of artificial neurons, a cluster-based neuromorphic device is a promising system with good costefficiency because of a simple fabrication process. This device functions using the formation and breakage of the connections (“synapses”) between clusters, driven by the bias voltage applied to the clusters. The mechanisms of the formation and breakage of these connections are thus of the utmost interest. In this thesis, the molecular dynamics simulation method is used to explore the mechanisms of the formation and breakage of the connections (“filaments”) between the clusters in a model of neuromorphic device. First, the Joule heating mechanism of filament breakage is explored using a model consisting of Au nanowire that connects two Au1415 clusters. Upon heating, the atoms of the nanofilament gradually aggregate towards the clusters, causing the middle of the wire to graduallythin and then suddenly break. Most of the system remains crystalline during this process, but the centre becomes molten. The terminal clusters increase the melting point of the nanowires by fixing them and act as recrystallisation regions. A strong dependence of the breaking temperature is found not only on the width of the nanowires but also their length and atomic structure. Secondly, the bridge formation and thermal breaking processes between Au1415 clusters on a graphite substrate are also simulated. The bridging process , which can heal a broken filament, is driven by diffusion of gold along the graphite substrate. The characteristic times of bridge formation are explored at elevated simulation temperatures to estimate the longer characteristic times of formation at room-temperature conditions. The width of the bridge formed has a power-law dependence on the simulation time, and the mechanism is a combination of diffusion and viscous flow. Simulations of bridgebreaking are also conducted and reveal the existence of a voltage threshold that must be reached to activate the breakage. The role of the substrate in the bridge formation and breakage processes is revealed as a medium of diffusion. Lastly, to explore future potential cluster materials, the thermal behaviour of Pb-Al core-shell clusters is studied. The core and shell are found to melt separately. In fact, the core atoms of nanoclusters tend to escape their shells and partially cover them, leading to a preference for a segregated state. The melting point of the core can either be depressed or elevated, depending on the thickness of the shell due to different mechanisms. E-Thesis Swansea, Wales, UK Neuromorphic Computing, Cluster-Based Neuromorphic Devices, Molecular Dynamics Simulation, Filament Formation and Breakage, Joule Heating Mechanism, Nanocluster, Nanowire, Diffusion, Melting 24 5 2023 2023-05-24 10.23889/SUthesis.63613 COLLEGE NANME COLLEGE CODE Swansea University Palmer, Richard E. and Pavloudis, Theodoros. Doctoral Ph.D Faculty of Science and Engineering, Swansea University 2023-09-29T10:31:52.7756477 2023-06-08T15:40:49.9014570 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering WENKAI WU 1 63613__27772__f0c5ea88ac354c9f9271cda21020149b.pdf 2023_Wu_W.final.63613.pdf 2023-06-08T15:49:09.6064878 Output 65654775 application/pdf E-Thesis – open access true Copyright: The Author, Wenkai Wu, 2023. true eng |
| title |
Molecular dynamics simulations of nanoclusters in neuromorphic systems |
| spellingShingle |
Molecular dynamics simulations of nanoclusters in neuromorphic systems WENKAI WU |
| title_short |
Molecular dynamics simulations of nanoclusters in neuromorphic systems |
| title_full |
Molecular dynamics simulations of nanoclusters in neuromorphic systems |
| title_fullStr |
Molecular dynamics simulations of nanoclusters in neuromorphic systems |
| title_full_unstemmed |
Molecular dynamics simulations of nanoclusters in neuromorphic systems |
| title_sort |
Molecular dynamics simulations of nanoclusters in neuromorphic systems |
| author_id_str_mv |
74bbf8e3606de3fcf398fc6151976b46 |
| author_id_fullname_str_mv |
74bbf8e3606de3fcf398fc6151976b46_***_WENKAI WU |
| author |
WENKAI WU |
| author2 |
WENKAI WU |
| format |
E-Thesis |
| publishDate |
2023 |
| institution |
Swansea University |
| doi_str_mv |
10.23889/SUthesis.63613 |
| college_str |
Faculty of Science and Engineering |
| hierarchytype |
|
| hierarchy_top_id |
facultyofscienceandengineering |
| hierarchy_top_title |
Faculty of Science and Engineering |
| hierarchy_parent_id |
facultyofscienceandengineering |
| hierarchy_parent_title |
Faculty of Science and Engineering |
| department_str |
School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering |
| document_store_str |
1 |
| active_str |
0 |
| description |
Neuromorphic computing is a new computing paradigm that deals with computing tasks using inter-connected artificial neurons inspired by the natural neurons in the human brain. This computational architecture is more efficient in performing many complex tasks such a pattern recognition and has promise at overcoming some of the limitations of conventional computers. Among the emerging types of artificial neurons, a cluster-based neuromorphic device is a promising system with good costefficiency because of a simple fabrication process. This device functions using the formation and breakage of the connections (“synapses”) between clusters, driven by the bias voltage applied to the clusters. The mechanisms of the formation and breakage of these connections are thus of the utmost interest. In this thesis, the molecular dynamics simulation method is used to explore the mechanisms of the formation and breakage of the connections (“filaments”) between the clusters in a model of neuromorphic device. First, the Joule heating mechanism of filament breakage is explored using a model consisting of Au nanowire that connects two Au1415 clusters. Upon heating, the atoms of the nanofilament gradually aggregate towards the clusters, causing the middle of the wire to graduallythin and then suddenly break. Most of the system remains crystalline during this process, but the centre becomes molten. The terminal clusters increase the melting point of the nanowires by fixing them and act as recrystallisation regions. A strong dependence of the breaking temperature is found not only on the width of the nanowires but also their length and atomic structure. Secondly, the bridge formation and thermal breaking processes between Au1415 clusters on a graphite substrate are also simulated. The bridging process , which can heal a broken filament, is driven by diffusion of gold along the graphite substrate. The characteristic times of bridge formation are explored at elevated simulation temperatures to estimate the longer characteristic times of formation at room-temperature conditions. The width of the bridge formed has a power-law dependence on the simulation time, and the mechanism is a combination of diffusion and viscous flow. Simulations of bridgebreaking are also conducted and reveal the existence of a voltage threshold that must be reached to activate the breakage. The role of the substrate in the bridge formation and breakage processes is revealed as a medium of diffusion. Lastly, to explore future potential cluster materials, the thermal behaviour of Pb-Al core-shell clusters is studied. The core and shell are found to melt separately. In fact, the core atoms of nanoclusters tend to escape their shells and partially cover them, leading to a preference for a segregated state. The melting point of the core can either be depressed or elevated, depending on the thickness of the shell due to different mechanisms. |
| published_date |
2023-05-24T10:31:54Z |
| _version_ |
1778363834380058624 |
| score |
11.016235 |