{"id":{"repo_id":"aachen","oai_identifier":"oai:publications.rwth-aachen.de:61417"},"canonical_url":"https://search.dev.ndltd.org/etd/aachen/oai:publications.rwth-aachen.de:61417","repository":{"repo_id":"aachen","name":"RWTH Aachen University","base_url":"https://publications.rwth-aachen.de/oai2d"},"display":{"title":"Strukturelle Phasenübergänge in TlH 2 PO 4 und Kristallstrukturen von Rb 0.7 Tl 0.3 H 2 PO 4 und Rb 0.5 Tl 0.5 H 2 PO 4","abstract":"For the investigation of crystal structures and the phase transitions of TlH2PO4 (TDP), single crystals have been synthesized. By the slow evaporation of the solution, large single crystals of Rb0.5Tl0.5H2PO4, which are proper to the neutron investigations and small single crystals of Rb0.7Tl0.3H2PO4 have been obtained. During the synthesis of TlH2PO4 Tl2HPO4, single crystals could be isolated and their structure was solved (Oh et al., 2004). The crystal structure of TDP II was newly solved at room temperature by neutron scattering and refined. In the phase TDP II two of three hydrogen atoms are disordered at room temperature. The crystal structure of low temperature phase of TDP (TDP III) was completely determined and refined at 210 K for the first time by neutron scattering. From this investigation, the space group and the enlarged elementary cell were confirmed. In the phase TDP – III all atoms occupy general positions. The H1 and H2 atoms of TDP – II structure freeze in one of their split positions. Thus all hydrogen bonds become asymmetric. TDP – III shows a completely ordered state of H – atoms. These ordered hydrogen atoms and formation of the portion of the covalent O – H bond cause a change of the electron density, which leads to a strong distortion of PO4 – groups. For the investigation of the phase transition TDP II – III with X – ray the high resolved powder diffractometer was used. No evidence indicating an additional phase transition was observed at low temperature. The TDP III structure remains until 7.7 K. By the observation of the split of the reflex (reflex broadening) the temperature of the phase transitions of 229.5 ± 0.5 K was determined. In the measurement no hysteresis was observed. With neutron the temperature dependence measurement on a single crystal was accomplished. Under the phase transition temperature Tc, a reflex broadening (Splitting) was observed. The splitting of the reflex due to the twinning goes completely back for T > Tc. The huge change of the reflex intensity is attributed at Tc to the decrease of the extinction. By the precipitous change of the reflex intensity the phase transition temperature could be exactly determined: Tc = 229.5 ± 0.5 K. No evidence for the hysteresis was found on the phase transition of first order. In this work the structures of the (Tl1-xRbx)H2PO4 – mixed crystals were investigated for the first time not only by X – ray but also by neutron at room temperature. Also in the Tl – Rb mixed crystals a partial H – ordering has been discovered. The protons show a dominant thermal vibration in the bond direction. The first type of hydrogen atom links each PO4 – groups in zigzag – like chains parallel to the c axis, while the second type links these chains along the a axis. Hydrogen bonds form a two – dimensional network parallel to the ac plane. The Tl+ – and/or Rb+ – ions lie between the zigzags – chains. The structure is composed of independent layers packed perpendicular to the b axis and linked together by Coulombic interactions with Tl+ and Rb+ ions. With this work the polymorphism of TDP / DTDP was determined to a large extent. Only the phase transition of the deuterated form DTDP has been known at 127 K and the crystal structure of DTDP at low temperature has not been yet determined until now.","abstract_html":"For the investigation of crystal structures and the phase transitions of TlH2PO4 (TDP), single crystals have been synthesized. By the slow evaporation of the solution, large single crystals of Rb0.5Tl0.5H2PO4, which are proper to the neutron investigations and small single crystals of Rb0.7Tl0.3H2PO4 have been obtained. During the synthesis of TlH2PO4 Tl2HPO4, single crystals could be isolated and their structure was solved (Oh et al., 2004). The crystal structure of TDP II was newly solved at room temperature by neutron scattering and refined. In the phase TDP II two of three hydrogen atoms are disordered at room temperature. The crystal structure of low temperature phase of TDP (TDP III) was completely determined and refined at 210 K for the first time by neutron scattering. From this investigation, the space group and the enlarged elementary cell were confirmed. In the phase TDP – III all atoms occupy general positions. The H1 and H2 atoms of TDP – II structure freeze in one of their split positions. Thus all hydrogen bonds become asymmetric. TDP – III shows a completely ordered state of H – atoms. These ordered hydrogen atoms and formation of the portion of the covalent O – H bond cause a change of the electron density, which leads to a strong distortion of PO4 – groups. For the investigation of the phase transition TDP II – III with X – ray the high resolved powder diffractometer was used. No evidence indicating an additional phase transition was observed at low temperature. The TDP III structure remains until 7.7 K. By the observation of the split of the reflex (reflex broadening) the temperature of the phase transitions of 229.5 ± 0.5 K was determined. In the measurement no hysteresis was observed. With neutron the temperature dependence measurement on a single crystal was accomplished. Under the phase transition temperature Tc, a reflex broadening (Splitting) was observed. The splitting of the reflex due to the twinning goes completely back for T > Tc. The huge change of the reflex intensity is attributed at Tc to the decrease of the extinction. By the precipitous change of the reflex intensity the phase transition temperature could be exactly determined: Tc = 229.5 ± 0.5 K. No evidence for the hysteresis was found on the phase transition of first order. In this work the structures of the (Tl1-xRbx)H2PO4 – mixed crystals were investigated for the first time not only by X – ray but also by neutron at room temperature. Also in the Tl – Rb mixed crystals a partial H – ordering has been discovered. The protons show a dominant thermal vibration in the bond direction. The first type of hydrogen atom links each PO4 – groups in zigzag – like chains parallel to the c axis, while the second type links these chains along the a axis. Hydrogen bonds form a two – dimensional network parallel to the ac plane. The Tl+ – and/or Rb+ – ions lie between the zigzags – chains. The structure is composed of independent layers packed perpendicular to the b axis and linked together by Coulombic interactions with Tl+ and Rb+ ions. With this work the polymorphism of TDP / DTDP was determined to a large extent. Only the phase transition of the deuterated form DTDP has been known at 127 K and the crystal structure of DTDP at low temperature has not been yet determined until now.","abstract_has_math":false,"creators":["Oh, In-Hwan"],"institution":"Publikationsserver der RWTH Aachen University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Heger, Gernot"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2005,"date_issued":"2005","date_published":"2005","updated_at":"2026-07-30T19:43:10Z","subjects":["info:eu-repo/classification/ddc/540","Thalliumverbindungen","Hydrogenphosphate","Kristallstrukturanalyse","Strukturelle Phasenumwandlung","Chemie","ferroelastisch","Phasenübergang","Neutronenbeugung","Röntgenbeugung"],"languages":["ger"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123082%22"],"render_values":[{"text":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123082%22","href":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123082%22","code":true}]}]},"links":{"outbound_url":"https://publications.rwth-aachen.de/record/61417","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Heger, Gernot"]},{"key":"dc:creator","label":"Author","values":["Oh, In-Hwan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:coverage","label":"Dc Coverage","values":["DE"]},{"key":"dc:date","label":"Dc Date","values":["2005"]},{"key":"dc:publisher","label":"Institution","values":["Publikationsserver der RWTH Aachen University"]},{"key":"dc:relation","label":"Dc Relation","values":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-11641"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["info:eu-repo/classification/ddc/540","Thalliumverbindungen","Hydrogenphosphate","Kristallstrukturanalyse","Strukturelle Phasenumwandlung","Chemie","ferroelastisch","Phasenübergang","Neutronenbeugung","Röntgenbeugung"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["ger"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/record/61417","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123082%22"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["For the investigation of crystal structures and the phase transitions of TlH2PO4 (TDP), single crystals have been synthesized. By the slow evaporation of the solution, large single crystals of Rb0.5Tl0.5H2PO4, which are proper to the neutron investigations and small single crystals of Rb0.7Tl0.3H2PO4 have been obtained. During the synthesis of TlH2PO4 Tl2HPO4, single crystals could be isolated and their structure was solved (Oh et al., 2004). The crystal structure of TDP II was newly solved at room temperature by neutron scattering and refined. In the phase TDP II two of three hydrogen atoms are disordered at room temperature. The crystal structure of low temperature phase of TDP (TDP III) was completely determined and refined at 210 K for the first time by neutron scattering. From this investigation, the space group and the enlarged elementary cell were confirmed. In the phase TDP – III all atoms occupy general positions. The H1 and H2 atoms of TDP – II structure freeze in one of their split positions. Thus all hydrogen bonds become asymmetric. TDP – III shows a completely ordered state of H – atoms. These ordered hydrogen atoms and formation of the portion of the covalent O – H bond cause a change of the electron density, which leads to a strong distortion of PO4 – groups. For the investigation of the phase transition TDP II – III with X – ray the high resolved powder diffractometer was used. No evidence indicating an additional phase transition was observed at low temperature. The TDP III structure remains until 7.7 K. By the observation of the split of the reflex (reflex broadening) the temperature of the phase transitions of 229.5 ± 0.5 K was determined. In the measurement no hysteresis was observed. With neutron the temperature dependence measurement on a single crystal was accomplished. Under the phase transition temperature Tc, a reflex broadening (Splitting) was observed. The splitting of the reflex due to the twinning goes completely back for T > Tc. The huge change of the reflex intensity is attributed at Tc to the decrease of the extinction. By the precipitous change of the reflex intensity the phase transition temperature could be exactly determined: Tc = 229.5 ± 0.5 K. No evidence for the hysteresis was found on the phase transition of first order. In this work the structures of the (Tl1-xRbx)H2PO4 – mixed crystals were investigated for the first time not only by X – ray but also by neutron at room temperature. Also in the Tl – Rb mixed crystals a partial H – ordering has been discovered. The protons show a dominant thermal vibration in the bond direction. The first type of hydrogen atom links each PO4 – groups in zigzag – like chains parallel to the c axis, while the second type links these chains along the a axis. Hydrogen bonds form a two – dimensional network parallel to the ac plane. The Tl+ – and/or Rb+ – ions lie between the zigzags – chains. The structure is composed of independent layers packed perpendicular to the b axis and linked together by Coulombic interactions with Tl+ and Rb+ ions. With this work the polymorphism of TDP / DTDP was determined to a large extent. Only the phase transition of the deuterated form DTDP has been known at 127 K and the crystal structure of DTDP at low temperature has not been yet determined until now."]},{"key":"dc:source","label":"Dc Source","values":["Aachen : Publikationsserver der RWTH Aachen University VII, 187 S. : Ill., graph. Darst. (2005). = Aachen, Techn. Hochsch., Diss., 2005"]},{"key":"dc:title","label":"Title","values":["Strukturelle Phasenübergänge in TlH 2 PO 4 und Kristallstrukturen von Rb 0.7 Tl 0.3 H 2 PO 4 und Rb 0.5 Tl 0.5 H 2 PO 4"]}]}],"canonical_facts":{"dc:contributor":["Heger, Gernot"],"dc:coverage":["DE"],"dc:creator":["Oh, In-Hwan"],"dc:date":["2005"],"dc:description":["For the investigation of crystal structures and the phase transitions of TlH2PO4 (TDP), single crystals have been synthesized. By the slow evaporation of the solution, large single crystals of Rb0.5Tl0.5H2PO4, which are proper to the neutron investigations and small single crystals of Rb0.7Tl0.3H2PO4 have been obtained. During the synthesis of TlH2PO4 Tl2HPO4, single crystals could be isolated and their structure was solved (Oh et al., 2004). The crystal structure of TDP II was newly solved at room temperature by neutron scattering and refined. In the phase TDP II two of three hydrogen atoms are disordered at room temperature. The crystal structure of low temperature phase of TDP (TDP III) was completely determined and refined at 210 K for the first time by neutron scattering. From this investigation, the space group and the enlarged elementary cell were confirmed. In the phase TDP – III all atoms occupy general positions. The H1 and H2 atoms of TDP – II structure freeze in one of their split positions. Thus all hydrogen bonds become asymmetric. TDP – III shows a completely ordered state of H – atoms. These ordered hydrogen atoms and formation of the portion of the covalent O – H bond cause a change of the electron density, which leads to a strong distortion of PO4 – groups. For the investigation of the phase transition TDP II – III with X – ray the high resolved powder diffractometer was used. No evidence indicating an additional phase transition was observed at low temperature. The TDP III structure remains until 7.7 K. By the observation of the split of the reflex (reflex broadening) the temperature of the phase transitions of 229.5 ± 0.5 K was determined. In the measurement no hysteresis was observed. With neutron the temperature dependence measurement on a single crystal was accomplished. Under the phase transition temperature Tc, a reflex broadening (Splitting) was observed. The splitting of the reflex due to the twinning goes completely back for T > Tc. The huge change of the reflex intensity is attributed at Tc to the decrease of the extinction. By the precipitous change of the reflex intensity the phase transition temperature could be exactly determined: Tc = 229.5 ± 0.5 K. No evidence for the hysteresis was found on the phase transition of first order. In this work the structures of the (Tl1-xRbx)H2PO4 – mixed crystals were investigated for the first time not only by X – ray but also by neutron at room temperature. Also in the Tl – Rb mixed crystals a partial H – ordering has been discovered. The protons show a dominant thermal vibration in the bond direction. The first type of hydrogen atom links each PO4 – groups in zigzag – like chains parallel to the c axis, while the second type links these chains along the a axis. Hydrogen bonds form a two – dimensional network parallel to the ac plane. The Tl+ – and/or Rb+ – ions lie between the zigzags – chains. The structure is composed of independent layers packed perpendicular to the b axis and linked together by Coulombic interactions with Tl+ and Rb+ ions. With this work the polymorphism of TDP / DTDP was determined to a large extent. Only the phase transition of the deuterated form DTDP has been known at 127 K and the crystal structure of DTDP at low temperature has not been yet determined until now."],"dc:identifier":["https://publications.rwth-aachen.de/record/61417","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123082%22"],"dc:language":["ger"],"dc:publisher":["Publikationsserver der RWTH Aachen University"],"dc:relation":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-11641"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:source":["Aachen : Publikationsserver der RWTH Aachen University VII, 187 S. : Ill., graph. Darst. (2005). = Aachen, Techn. Hochsch., Diss., 2005"],"dc:subject":["info:eu-repo/classification/ddc/540","Thalliumverbindungen","Hydrogenphosphate","Kristallstrukturanalyse","Strukturelle Phasenumwandlung","Chemie","ferroelastisch","Phasenübergang","Neutronenbeugung","Röntgenbeugung"],"dc:title":["Strukturelle Phasenübergänge in TlH 2 PO 4 und Kristallstrukturen von Rb 0.7 Tl 0.3 H 2 PO 4 und Rb 0.5 Tl 0.5 H 2 PO 4"],"dc:type":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-30T19:43:10Z"}