Chemical bond and electronic states in calcium silicides: Theory and comparison with synchrotron-radiation photoemission

Electronic and structural properties of superconductingMgB2,CaSi2Satta1, Profeta2, Bernardini3 et al. 2001Phys. Rev. B15313931View full textAdd to dashboardCite

“…The occurrence of this structural phase transition indicates that Si shifts from an sp 3 to an sp 2 -like hybridization, and experiment points to a clear enhancement of T c with high pressure [15]. Many electronic structure studies have been carried out for the different phases [17][18][19] of disilicides. CaSi 2 in the AlB 2 structure was studied by Kusakabe et al [20], but a final answer on the stability of this phase under pressure is still lacking.…”

Epitaxial relations, crystalline structure and defects in the double Si(111)/hR6 CaSi2/Si(111) heterostructures

“…3(a), area (1)) with epitaxial relations: hR6-CaSi2[100]||Si [1][2][3][4][5][6][7][8][9][10] and hR6-CaSi2(001)||Si(111). The identification of the SA FFT pattern for area (1) results in the un-defective CaSi2 layer growth on Si(111)7x7 surface without stacking faults in 3-4 unit cell thickness.…”

“…It is known that CaSi2 as a compound in the Ca-Si system with a maximum silicon concentration [1], it is a metal according to the theoretical work [3]. At atmospheric pressure a rhombohedral CaSi2 structure with a space group R-3m and two modifications hR3 and hR6 has been observed [4].…”

Investigation of structural, elastic, and lattice-dynamical properties of Ca2Si, Ca2Ge, and Ca2Sn based on first-principles density functional theory

“…These values are larger than the static Mulliken charge values for Ca 2 X shown in Table 5, but are close to the nominal charges (+2 for Ca and À4 for X) in a purely ionic crystal. Bisi et al [41] investigated the electronic structure and chemical bonds of Ca-Si compounds theoretically as well as experimentally and they found a degree of ionic character is present concurrently with covalent interactions due to the hybridization of Ca's s-p-d orbitals with Si's 3p. Therefore, the difference between the dynamic and static charges may be ascribed to the mixed covalent-ionic bonding of Ca-X.…”

“…The average phonon frequency for Ca I is higher than that of Ca II, and it also has a strong dependence on the type of X atom. Bisi et al [41] reported the coordination numbers and interatomic distances for Ca 2 Si. They discussed in detail the geometric differences between the Ca I and Ca II atoms in Ca 2 Si, finding that the average distance for the Ca II -nearest neighbor X is greater than that of the Ca I -nearest neighbor X; and the number of nearest neighbor X atoms for Ca I is larger than for Ca II .…”