biostudies-literatureKogan SNSFUCLA Office of Advanced Research Computing's Research Technology GroupBridges-2 at Pittsburgh Supercomputing Centere202501536https://www.ebi.ac.uk/biostudies/studies/S-EPMC12415313biostudies-literatureUnknown31(50)The influence of metal d orbitals on the high-pressure structures of CaO, SrO, and BaO are investigated with DFT calculations and chemical bonding analysis. CaO and SrO undergo the B1-B2 transition, from the rock salt structure to the caesium chloride structure, while BaO undergoes a sequence of transitions from B1-B8, the NiAs structure, and then B8 - dB2, a distorted form of B2. DFT calculations of bond strengths show that the B8 and dB2 structures are stabilized relative to B1 and B2 by metal-oxygen covalency through the metal d orbitals. In BaO covalency outweighs electrostatics because of the large 5d orbitals of Ba, so the unique B8 and dB2 structures form. This marks an important expansion of the importance of d orbitals in group II chemistry.Chemistry (Weinheim an der Bergstrasse, Germany)5d Orbital Covalency Controls the High-Pressure Polymorphism of BaO.PMC12415313#2138307CHE240146#2137603#2138259#2138286#2138296Alexandrova ANKogan SMorgan HWTfalse5d Orbital Covalency Controls the High-Pressure Polymorphism of BaO.The influence of metal d orbitals on the high-pressure structures of CaO, SrO, and BaO are investigated with DFT calculations and chemical bonding analysis. CaO and SrO undergo the B1-B2 transition, from the rock salt structure to the caesium chloride structure, while BaO undergoes a sequence of transitions from B1-B8, the NiAs structure, and then B8 - dB2, a distorted form of B2. DFT calculations of bond strengths show that the B8 and dB2 structures are stabilized relative to B1 and B2 by metal-oxygen covalency through the metal d orbitals. In BaO covalency outweighs electrostatics because of the large 5d orbitals of Ba, so the unique B8 and dB2 structures form. This marks an important expansion of the importance of d orbitals in group II chemistry.2025-01-01T00:00:00Z2025 Sep2026-06-02T00:36:16.27Z2026-05-24T03:07:14.203ZS-EPMC124153134058372310.1002/chem.202501536