{"id":{"repo_id":"ku","oai_identifier":"oai:kuscholarworks.ku.edu:1808/39112"},"canonical_url":"https://search.dev.ndltd.org/etd/ku/oai:kuscholarworks.ku.edu:1808/39112","repository":{"repo_id":"ku","name":"University of Kansas","base_url":"https://kuscholarworks.ku.edu/server/oai/request"},"display":{"title":"Structure and thermodynamics of solid/fluid interfaces: simulation and theory","abstract":"Interfaces between different material phases are omnipresent and their properties play animportant role in a wide range of applications. However, experimentally probing the structure and thermodynamic properties of interfaces presents great challenges due to the limited extent of the interfacial region. In this dissertation, I present simulation studies of several interfacial systems to characterize their structure and thermodynamics. In the first part of this dissertation, results from Monte Carlo simulation of the hard-disk fluid at hard walls of various shapes are presented. The effect of surface curvature on the interfacial free energy, , and the interfacial excess volume, vex, are studied in detail using simulation and virial expansions in the low density limit. Comparisons are made to the predictions of Morphometric Thermodynamics (MT), an analytical theory which predicts that in two dimensional systems the curvature dependence of is completely specified by a linear dependence on the mean curvature of the surface, C. It is found that for the hard-disk fluid / hard wall system, MT is applicable over a large range of fluid conditions. Breakdowns in this linear dependence on C are only observed at high densities or for the hard-disk fluid in severe confinement. The simulation results presented in Part I of this dissertation are, to the author’s knowledge, the first to directly evaluate the interfacial free energy of the hard-disk fluid at hard walls. This data provides a much needed benchmark with which to test approximate theories for the interfacial thermodynamics of this system. The simulation results and the accompanying analysis of the virial expansion for these systems show that, while Morphometric Thermodynamics has a surprisingly large range of applicability, higher order curvature corrections to the interfacial free energy cannot be accounted for by simple truncated expansions in the curvature. The work of this thesis shows that any future work which attempts to move beyond the morphometric or similar approaches will require a more sophisticated accounting of the curvature effects than has been attempted heretofore. The second part of this dissertation presents simulations using reactive force fields of two chemical systems of industrial relevance. First, a new ReaxFF force field is developed to model silica-supported chromium catalysts. To this end, a new genetic algorithm optimization software is developed to allow global fitting of parameters for the newly developed force field. A proof-of-concept is presented, along with suggestions for further refinement of the force field. Second, the Al(l)/Al2O3(s) interface is studied using the COMB3 and ReaxFF reactive force fields. It is found that the currently available implementation of COMB3 has severe issues of energy conservation. On the other hand, the ReaxFF force field is unable to properly model a stable interface for this system. Therefore, results for an interface with a fixed alumina substrate are presented. It is found that simulations using a fixed alumina substrate gives some insight to the ordering of the Al liquid observed in experimental studies of this interface. Part II of this dissertation demonstrate both the power and drawbacks of reactive force field models. It is shown that while reactive force fields can describe complex chemical behavior, they can also fail quite severely. Many current parameterizations of reactive force fields are based on single parameter search methods, which have a strong likelihood of becoming trapped in local minima. Using more robust training methods, such as genetic algorithms should be considered for complex force fields with many parameters. It is also demonstrated that even well established reactive force fields that have seen wide adoption in the literature need to be evaluated more critically. The COMB3 implementation currently available shows extreme issues with conservation of energy and linear momentum. Understanding of the origin of these issues should be a priority in the reactive force field community.","abstract_html":"Interfaces between different material phases are omnipresent and their properties play animportant role in a wide range of applications. However, experimentally probing the structure and thermodynamic properties of interfaces presents great challenges due to the limited extent of the interfacial region. In this dissertation, I present simulation studies of several interfacial systems to characterize their structure and thermodynamics. In the first part of this dissertation, results from Monte Carlo simulation of the hard-disk fluid at hard walls of various shapes are presented. The effect of surface curvature on the interfacial free energy, , and the interfacial excess volume, vex, are studied in detail using simulation and virial expansions in the low density limit. Comparisons are made to the predictions of Morphometric Thermodynamics (MT), an analytical theory which predicts that in two dimensional systems the curvature dependence of is completely specified by a linear dependence on the mean curvature of the surface, C. It is found that for the hard-disk fluid / hard wall system, MT is applicable over a large range of fluid conditions. Breakdowns in this linear dependence on C are only observed at high densities or for the hard-disk fluid in severe confinement. The simulation results presented in Part I of this dissertation are, to the author’s knowledge, the first to directly evaluate the interfacial free energy of the hard-disk fluid at hard walls. This data provides a much needed benchmark with which to test approximate theories for the interfacial thermodynamics of this system. The simulation results and the accompanying analysis of the virial expansion for these systems show that, while Morphometric Thermodynamics has a surprisingly large range of applicability, higher order curvature corrections to the interfacial free energy cannot be accounted for by simple truncated expansions in the curvature. The work of this thesis shows that any future work which attempts to move beyond the morphometric or similar approaches will require a more sophisticated accounting of the curvature effects than has been attempted heretofore. The second part of this dissertation presents simulations using reactive force fields of two chemical systems of industrial relevance. First, a new ReaxFF force field is developed to model silica-supported chromium catalysts. To this end, a new genetic algorithm optimization software is developed to allow global fitting of parameters for the newly developed force field. A proof-of-concept is presented, along with suggestions for further refinement of the force field. Second, the Al(l)/Al2O3(s) interface is studied using the COMB3 and ReaxFF reactive force fields. It is found that the currently available implementation of COMB3 has severe issues of energy conservation. On the other hand, the ReaxFF force field is unable to properly model a stable interface for this system. Therefore, results for an interface with a fixed alumina substrate are presented. It is found that simulations using a fixed alumina substrate gives some insight to the ordering of the Al liquid observed in experimental studies of this interface. Part II of this dissertation demonstrate both the power and drawbacks of reactive force field models. It is shown that while reactive force fields can describe complex chemical behavior, they can also fail quite severely. Many current parameterizations of reactive force fields are based on single parameter search methods, which have a strong likelihood of becoming trapped in local minima. Using more robust training methods, such as genetic algorithms should be considered for complex force fields with many parameters. It is also demonstrated that even well established reactive force fields that have seen wide adoption in the literature need to be evaluated more critically. The COMB3 implementation currently available shows extreme issues with conservation of energy and linear momentum. Understanding of the origin of these issues should be a priority in the reactive force field community.","abstract_has_math":false,"creators":["Martin, Seth Curtis"],"institution":"University of Kansas","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Laird, Brian B"],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-01-01","date_published":"2021-01-01","updated_at":"2026-07-24T02:45:31Z","subjects":["Physical chemistry","Thermodynamics","Computational chemistry","Alumina","Hard disks","Interfaces","Morphometric thermodynamics","Phillips catalyst","Surfaces"],"languages":["en"],"rights":["Copyright held by the author."],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["http://dissertations.umi.com/ku:17855"],"render_values":[{"text":"http://dissertations.umi.com/ku:17855","href":"http://dissertations.umi.com/ku:17855","code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/1808/39112","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Laird, Brian B"]},{"key":"dc:creator","label":"Author","values":["Martin, Seth Curtis"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-04-25T03:46:12Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-04-25T03:46:12Z"]},{"key":"dc:date.issued","label":"Date","values":["2021-01-01"]},{"key":"dc:publisher","label":"Institution","values":["University of Kansas"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physical chemistry","Thermodynamics","Computational chemistry","Alumina","Hard disks","Interfaces","Morphometric thermodynamics","Phillips catalyst","Surfaces"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright held by the author."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["http://dissertations.umi.com/ku:17855"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/1808/39112"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Interfaces between different material phases are omnipresent and their properties play animportant role in a wide range of applications. However, experimentally probing the structure and thermodynamic properties of interfaces presents great challenges due to the limited extent of the interfacial region. In this dissertation, I present simulation studies of several interfacial systems to characterize their structure and thermodynamics. In the first part of this dissertation, results from Monte Carlo simulation of the hard-disk fluid at hard walls of various shapes are presented. The effect of surface curvature on the interfacial free energy, , and the interfacial excess volume, vex, are studied in detail using simulation and virial expansions in the low density limit. Comparisons are made to the predictions of Morphometric Thermodynamics (MT), an analytical theory which predicts that in two dimensional systems the curvature dependence of is completely specified by a linear dependence on the mean curvature of the surface, C. It is found that for the hard-disk fluid / hard wall system, MT is applicable over a large range of fluid conditions. Breakdowns in this linear dependence on C are only observed at high densities or for the hard-disk fluid in severe confinement. The simulation results presented in Part I of this dissertation are, to the author’s knowledge, the first to directly evaluate the interfacial free energy of the hard-disk fluid at hard walls. This data provides a much needed benchmark with which to test approximate theories for the interfacial thermodynamics of this system. The simulation results and the accompanying analysis of the virial expansion for these systems show that, while Morphometric Thermodynamics has a surprisingly large range of applicability, higher order curvature corrections to the interfacial free energy cannot be accounted for by simple truncated expansions in the curvature. The work of this thesis shows that any future work which attempts to move beyond the morphometric or similar approaches will require a more sophisticated accounting of the curvature effects than has been attempted heretofore. The second part of this dissertation presents simulations using reactive force fields of two chemical systems of industrial relevance. First, a new ReaxFF force field is developed to model silica-supported chromium catalysts. To this end, a new genetic algorithm optimization software is developed to allow global fitting of parameters for the newly developed force field. A proof-of-concept is presented, along with suggestions for further refinement of the force field. Second, the Al(l)/Al2O3(s) interface is studied using the COMB3 and ReaxFF reactive force fields. It is found that the currently available implementation of COMB3 has severe issues of energy conservation. On the other hand, the ReaxFF force field is unable to properly model a stable interface for this system. Therefore, results for an interface with a fixed alumina substrate are presented. It is found that simulations using a fixed alumina substrate gives some insight to the ordering of the Al liquid observed in experimental studies of this interface. Part II of this dissertation demonstrate both the power and drawbacks of reactive force field models. It is shown that while reactive force fields can describe complex chemical behavior, they can also fail quite severely. Many current parameterizations of reactive force fields are based on single parameter search methods, which have a strong likelihood of becoming trapped in local minima. Using more robust training methods, such as genetic algorithms should be considered for complex force fields with many parameters. It is also demonstrated that even well established reactive force fields that have seen wide adoption in the literature need to be evaluated more critically. The COMB3 implementation currently available shows extreme issues with conservation of energy and linear momentum. Understanding of the origin of these issues should be a priority in the reactive force field community."]},{"key":"dc:title","label":"Title","values":["Structure and thermodynamics of solid/fluid interfaces: simulation and theory"]}]}],"canonical_facts":{"dc:contributor.advisor":["Laird, Brian B"],"dc:creator":["Martin, Seth Curtis"],"dc:date.accessioned":["2026-04-25T03:46:12Z"],"dc:date.available":["2026-04-25T03:46:12Z"],"dc:date.issued":["2021-01-01"],"dc:description.abstract":["Interfaces between different material phases are omnipresent and their properties play animportant role in a wide range of applications. However, experimentally probing the structure and thermodynamic properties of interfaces presents great challenges due to the limited extent of the interfacial region. In this dissertation, I present simulation studies of several interfacial systems to characterize their structure and thermodynamics. In the first part of this dissertation, results from Monte Carlo simulation of the hard-disk fluid at hard walls of various shapes are presented. The effect of surface curvature on the interfacial free energy, , and the interfacial excess volume, vex, are studied in detail using simulation and virial expansions in the low density limit. Comparisons are made to the predictions of Morphometric Thermodynamics (MT), an analytical theory which predicts that in two dimensional systems the curvature dependence of is completely specified by a linear dependence on the mean curvature of the surface, C. It is found that for the hard-disk fluid / hard wall system, MT is applicable over a large range of fluid conditions. Breakdowns in this linear dependence on C are only observed at high densities or for the hard-disk fluid in severe confinement. The simulation results presented in Part I of this dissertation are, to the author’s knowledge, the first to directly evaluate the interfacial free energy of the hard-disk fluid at hard walls. This data provides a much needed benchmark with which to test approximate theories for the interfacial thermodynamics of this system. The simulation results and the accompanying analysis of the virial expansion for these systems show that, while Morphometric Thermodynamics has a surprisingly large range of applicability, higher order curvature corrections to the interfacial free energy cannot be accounted for by simple truncated expansions in the curvature. The work of this thesis shows that any future work which attempts to move beyond the morphometric or similar approaches will require a more sophisticated accounting of the curvature effects than has been attempted heretofore. The second part of this dissertation presents simulations using reactive force fields of two chemical systems of industrial relevance. First, a new ReaxFF force field is developed to model silica-supported chromium catalysts. To this end, a new genetic algorithm optimization software is developed to allow global fitting of parameters for the newly developed force field. A proof-of-concept is presented, along with suggestions for further refinement of the force field. Second, the Al(l)/Al2O3(s) interface is studied using the COMB3 and ReaxFF reactive force fields. It is found that the currently available implementation of COMB3 has severe issues of energy conservation. On the other hand, the ReaxFF force field is unable to properly model a stable interface for this system. Therefore, results for an interface with a fixed alumina substrate are presented. It is found that simulations using a fixed alumina substrate gives some insight to the ordering of the Al liquid observed in experimental studies of this interface. Part II of this dissertation demonstrate both the power and drawbacks of reactive force field models. It is shown that while reactive force fields can describe complex chemical behavior, they can also fail quite severely. Many current parameterizations of reactive force fields are based on single parameter search methods, which have a strong likelihood of becoming trapped in local minima. Using more robust training methods, such as genetic algorithms should be considered for complex force fields with many parameters. It is also demonstrated that even well established reactive force fields that have seen wide adoption in the literature need to be evaluated more critically. The COMB3 implementation currently available shows extreme issues with conservation of energy and linear momentum. Understanding of the origin of these issues should be a priority in the reactive force field community."],"dc:identifier.other":["http://dissertations.umi.com/ku:17855"],"dc:identifier.uri":["https://hdl.handle.net/1808/39112"],"dc:language.iso":["en"],"dc:publisher":["University of Kansas"],"dc:rights":["Copyright held by the author."],"dc:subject":["Physical chemistry","Thermodynamics","Computational chemistry","Alumina","Hard disks","Interfaces","Morphometric thermodynamics","Phillips catalyst","Surfaces"],"dc:title":["Structure and thermodynamics of solid/fluid interfaces: simulation and theory"],"dc:type":["Dissertation"]},"updated_at":"2026-07-24T02:45:31Z"}