Thermodynamic, elastic, and vibrational (IR/Raman) behavior of mixed type-AB carbonated hydroxylapatite by density functional theory

The present investigation reports the equation of state, thermodynamic, and thermoelastic properties of type AB carbonated apatite [CAp-AB, Ca10(CO3)B(PO4)5(CO3)A, space group P1], as obtained from density functional theory simulations and the quasi-harmonic approximation. The static (0 K) third-order Birch-Murnaghan equation of state resulted in the parameters K0 = 104.3(8) GPa, K′ = 4.3(1), and V0 = 517.9(2) Å3, whereas at room temperature (300 K) they were KT = 101.98 GPa, K′ = 4.12, and V0 = 524.486 GPa. Thermodynamics and thermoelasticity were calculated in the temperature range 0-800 K and between 0 and 30 GPa. Furthermore, the dependence of the infrared/Raman spectra of type-AB carbonated apatite with pressure is also reported, which could be useful for researchers interested in vibrational spectroscopy. The theoretical results corroborate the few experimental ones on a similar type-AB carbonated hydroxylapatite and provide further details over wide pressure and temperature ranges on the elastic, thermodynamic, and infrared/Raman properties of this important mineral found in both geological and biological environments.