Thesis

Computer simulation of the growth of ice structures under astronomical conditions

Creator
Rights statement
Awarding institution
  • University of Strathclyde
  • Scottish Universities Physics Alliance
Date of award
  • 2016
Thesis identifier
  • T14547
Person Identifier (Local)
  • 200968878
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • As part of the diffuse interstellar medium, water molecules contribute extensively to the chemical properties of astronomical environments, both in the gaseous and adsorbed state. Along with carbon monoxide, water is expected to deposit on silicate dust grains in space, forming icy films which may provide a substrate for exotic, low-temperature surface chemistry and act as a reservoir for further deposited species. On account of the nature of its aggregation - vapour deposition over millions of years in environments as cold as 10K - the water ice is not expected to form a crystalline structure as under terrestrial conditions, but rather a metastable glass: 'amorphous solid water', ASW. In this work we used molecular dynamics to model the deposition of water onto cold substrates of both silica (representing a bare grain surface) and cubic crystalline ice (representing an ice-covered grain migrating back from warmer regions), with the intention of understanding film growth and properties in circumstellar environments. The water was injected at different energies, onto substrates of different temperatures, to determine what effect the thermal conditions of the water / substrate interaction had on the ice films formed.Significant differences were observed between those molecules deposited under the coldest (10K deposition on 10K substrate) and warmest (300K deposition on 130K substrate) regimes. Cold aggregation, as would be expected in the core of a dark molecular cloud, produced tall, filamentous structures with cavities. Meanwhile, warmer conditions produced dense, comparatively flat films.
Resource Type
Note
  • Error on cover of print copy. Degree awarded is Master of Philosophy not Master of Research.
DOI
Date Created
  • 2016
Former identifier
  • 9912547786902996

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