Thermodynamics Research Center / ThermoML | Thermochimica Acta

Order disorder phase transition in crystalline di-tert-butylphosphinic acid dimer: The role of the ice rules and quantum tunneling

Ueda, K.[Kouhei], Oguni, M.[Masaharu]
Thermochim. Acta 2012, 532, 183-186
ABSTRACT
Heat capacities of di-tert-butylphosphinic acid (abbreviated as DTPA) crystal were measured by adiabatic calorimetry. Phase transition of a second-order type was discovered at 37.8 K. The entropy of the transition was estimated to be 2.6 J K-1 mol-1, and the magnitude was interpreted as suggesting that the transition is attributed to the order disorder process of the hydrogen-bonded protons of a DTPA dimer and that the protons rearrange with always keeping the ice rules. It was discussed that the real state of the protons should be described on the consideration of the tunneling between the two configurations which are represented classically as each proton is located close to either of the two oxygen atoms forming a hydrogen bond.
Compounds
# Formula Name
1 C8H19O2P di-tert-butylphosphinic acid
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • POMD
  • 1
  • Triple point temperature, K ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Gas
  • VISOBS
  • 1
  • POMD
  • 1
  • Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Gas
  • Adiabatic calorimetry
  • 1
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 1
  • Temperature, K; Crystal 1
  • Pressure, kPa; Crystal 1
  • Crystal 1
  • ADIACNV
  • 143
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 2
  • Temperature, K; Crystal 2
  • Pressure, kPa; Crystal 2
  • Crystal 2
  • ADIACNV
  • 40
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal 1
  • Temperature, K; Crystal 1
  • Pressure, kPa; Crystal 1
  • Crystal 1
  • ADIACNV
  • 45