Table 1 Ab initio energies of the tetragonal phase.

From: Order from disorder phenomena in BaCoS2

Spin and orbital configurations

E(Kelvin)

#

C-AFS-a-C(xyyx)

0

T0

G-AFS-a-C(xyyx)

2

T1

C-AFS-a-G(xyyx)

14

T2

G-AFS-a-G(xyyx)

22

T3

G-AFS-a-G(xyxy)

50

T4

C-AFS-a-G(xyxy)

52

T5

C-AFS-a-C(xyxy)

52

T6

C-AFS-a-C(yyyy)

57

T7

G-AFS-a-C(xyxy)

64

T8

G-AFS-a-C(yyyy)

73

T9

C-AFS-a-G(xxyy)

79

T10

C-AFS-a-G(yyyy)

86

T11

G-AFS-a-G(yyyy)

89

T12

G-AFS-a-C(xxyy)

89

T13

C-AFS-a-C(xxyy)

93

T14

G-AFS-a-G(xxyy)

95

T15

G-AFS-a-C(xxxx)

171

T16

C-AFS-a-C(xxxx)

176

T17

  1. Hubbard-U corrected density functional theory (DFT + U) energies (U = 2.8 eV) in Kelvin and per formula unit of the low-lying spin and orbital configurations in the tetragonal structure with an 8-site unit cell, assuming an antiferromagnetic stripe order along a (AFS-a), being degenerate with AFS-b. The lowest energy state sets the zero of energy. Note that some states are doubly degenerate, for instance C(xyyx) is degenerate with C(yxxy) as well as G(yyyy) is degenerate with G(xxxx), and thus we just indicate one of them. Moreover, the table includes also configurations not allowed by the Cmme orthorhombic space group, which, nonetheless, represent alternative symmetry-breaking paths from the tetragonal structure. Each state is labelled by Tn, T referring to the tetragonal phase and n being the ascending order in energy.
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