The advent of computers brought a profound change in the way the practical problems in the physics of materials are addressed. Within the last decade, a rapidly evolving area of research is oriented towards interfacing the existing numerical tools in an optimized way, by explicitly taking advantage of the specifics of the problem, the so called "hybrid" approach. The Classical Molecular Dynamics (CMD) method holds a central position among computational methods for modeling on different levels of physical behavior; its two main limitations are the accuracy of the force-fields used, and accessible time scale. In this work, a new methodology was constructed to improve a force-field quality by matching it to a quantum model via mapping a complex many-body situation to a much reduced description of important local geometries. It was tested on a system of a water molecule interacting with hematite surface and a 66% reduction in the force mismatch was achieved. Also, a strategy of efficiently improving radial data fitting is found, where fit-functions are defined on a set of overlapping radial zones and where a specific post-processing numerical demand on the fitting data is required. It was incorporated, tested and applied to the DVM density-functional code and showed that the fitting error of the radial degrees of freedom can be efficiently removed for all practical purposes. Two different systems with concurrent Poisson and Newtonian evolution were analyzed in attempt go to beyond the CMD accessible time. Polymerization and self-assembly of thin molecular films on a quartz surface was modeled where local hydrogen bonding was used as an indicator of local configurational relaxation, and as a guide to a polymerization process. The results present a consistent picture which contradicts previous interpretation of experimental data. Also, a study of glass-forming glycerol liquid diffusion was conducted on a temperature range inaccessible to CMD. Atoms were artificially accelerated to have their diffusion measured while the local hydrogen bonding was used to re-establish the appropriate time counting. The results are speculative, however they do suggest a possibility for hydrogen-bonding related Poisson rates, when appropriately filtered, to be used to map out the time scale of diffusion over more then three orders of magnitude.

Last modified

• 10/02/2018

Creator

• ljubomir Miljacic

DOI

• https://doi.org/10.21985/N2TM86

Subject

• Physics and Astronomy

Keyword

• Physics
• Condensed Matter

Date created

• 2008-12-05

Resource type

• Dissertation

Rights statement

• In Copyright