title: Role of relativity in high-pressure phase transitions of thallium.
abstract: We demonstrate the relativistic effects in high-pressure phase transitions of heavy element thallium. The known first phase transition from h.c.p. to f.c.c. is initially investigated by various relativistic levels and exchange-correlation functionals as implemented in FPLO method, as well as scalar relativistic scheme within PAW formalism. The electronic structure calculations are interpreted from the perspective of energetic stability and electronic density of states. The full relativistic scheme (FR) within L(S)DA performs to be the scheme that resembles mostly with experimental results with a transition pressure of 3 GPa. The s-p hybridization and the valence-core overlapping of 6s and 5d states are the primary reasons behind the f.c.c. phase occurrence. A recent proposed phase, i.e., a body-centered tetragonal (b.c.t.) phase, is confirmed with a small distortion from the f.c.c. phase. We have also predicted a reversible b.c.t. → f.c.c. phase transition at 800 GPa. This finding has been suggested that almost all the III-A elements (Ga, In and Tl) exhibit the b.c.t. → f.c.c. phase transition at extremely high pressure.
authors.affiliation: Department of Physics, Mahidol Wittayanusorn School, Nakhon Pathom 73170, Thailand.|Thailand Center of Excellence in Physics, Commission on Higher Education, Bangkok 10400, Thailand.
authors.forename: Komsilp
authors.initials: K
authors.lastname: Kotmool
authors.affiliation: Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala, Sweden.
authors.forename: Sudip
authors.initials: S
authors.lastname: Chakraborty
authors.affiliation: Thailand Center of Excellence in Physics, Commission on Higher Education, Bangkok 10400, Thailand.|Extreme Conditions Physics Research Laboratory (ECPRL), Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Thiti
authors.initials: T
authors.lastname: Bovornratanaraks
authors.affiliation: Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala, Sweden.|Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm, Sweden.
authors.forename: Rajeev
authors.initials: R
authors.lastname: Ahuja