TY - JOUR

T1 - Phase relations in calcium silicates, Ca2SiO4 and CaSi2O5, investigated by first-principle quasi-harmonic theory

AU - Sagatova, Dinara N.

AU - Sagatov, Nursultan E.

AU - Shatskiy, Anton F.

AU - Gavryushkin, Pavel N.

AU - Litasov, Konstantin D.

N1 - This study was funded by the Russian Science Foundation , project no. 23-73-10114 ( https://rscf.ru/en/project/23-73-10114/ ). The calculations were performed using resources provided by the Novosibirsk State University Supercomputer Center.

PY - 2025/8

Y1 - 2025/8

N2 - In this work, we have studied in detail the phase relationships in Ca2SiO4 and CaSi2O5 compounds within the density functional theory using the quasi-harmonic approximation. According to the obtained results, for Ca2SiO4, with increasing pressure, two polymorphic transitions are observed: γ→β at 4 GPa and β→I4/mmm at 17 GPa. For the first time, the stability limits of the high-pressure modification Ca2SiO4-I4/mmm have been calculated. Our results indicate that the Ca2SiO4-I4/mmm remains stable up to a pressure of 65 GPa, where it decomposed into the association CaSiO3+CaO. Based on the calculations of phonon spectra, the dynamic stability of Ca2SiO4-I4/mmm at 0 GPa was established, which indicates that it likely may even be recovered at ambient conditions. Calculations of phase relations in CaSi2O5 showed that this compound can be formed in the pressure range of 5–16 GPa and 300 K from the mixture of CaSiO3+SiO2 and is stable in the C2/c structure. Our results indicate that the previously known CaSi2O5-P1̄ structure is transformed into the CaSi2O5-P1̄-II structure under compression in the range of 4–5 GPa. The P1̄-II modification is low-temperature phase and could be formed below 300 K in a narrow pressure range of 12.5–15.2 GPa.

AB - In this work, we have studied in detail the phase relationships in Ca2SiO4 and CaSi2O5 compounds within the density functional theory using the quasi-harmonic approximation. According to the obtained results, for Ca2SiO4, with increasing pressure, two polymorphic transitions are observed: γ→β at 4 GPa and β→I4/mmm at 17 GPa. For the first time, the stability limits of the high-pressure modification Ca2SiO4-I4/mmm have been calculated. Our results indicate that the Ca2SiO4-I4/mmm remains stable up to a pressure of 65 GPa, where it decomposed into the association CaSiO3+CaO. Based on the calculations of phonon spectra, the dynamic stability of Ca2SiO4-I4/mmm at 0 GPa was established, which indicates that it likely may even be recovered at ambient conditions. Calculations of phase relations in CaSi2O5 showed that this compound can be formed in the pressure range of 5–16 GPa and 300 K from the mixture of CaSiO3+SiO2 and is stable in the C2/c structure. Our results indicate that the previously known CaSi2O5-P1̄ structure is transformed into the CaSi2O5-P1̄-II structure under compression in the range of 4–5 GPa. The P1̄-II modification is low-temperature phase and could be formed below 300 K in a narrow pressure range of 12.5–15.2 GPa.

KW - Ca2SiO4

KW - CaSi2O5

KW - Calcium silicates

KW - Density functional theory

KW - P–T phase diagram

UR - https://www.mendeley.com/catalogue/65bb22f3-25e6-3c2a-8ec5-a509715bb474/

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-105009154755&origin=inward&txGid=dfc9a36f963cd95552d539122e06d6c8

U2 - 10.1016/j.commatsci.2025.114044

DO - 10.1016/j.commatsci.2025.114044

M3 - Article

VL - 258

JO - Computational Materials Science

JF - Computational Materials Science

SN - 0927-0256

M1 - 114044

ER -