Energetics of C11b, C40, C54, and C49 structures in transition-metal disilicides

1991 ◽  
Vol 6 (7) ◽  
pp. 1512-1517 ◽  
Author(s):  
A.E. Carlsson ◽  
P.J. Meschter
Keyword(s):  
Transition Metal ◽  
Spherical Wave ◽  
Energy Difference ◽  
Group Iv ◽  
Computational Method ◽  
Electronic Density ◽  
Band Structure Calculations ◽  
Atomic Coordination ◽  
Metal Aluminides ◽  
Structure Calculations

The relative energies of the related C11b, C40, and C54 crystal structures of group IV–VII transition-metal disilicides are obtained by ab initio self-consistent band-structure calculations using the augmented-spherical-wave (ASW) method. The structural energy differences among these three structures correlate strongly with d-band filling, with C40 being stabilized relative to C54 and C11b relative to C40 as the transition-metal d-electron count increases. The C40/C11b energy difference is <0.05 eV/atom only for CrSi2 and MoSi2. Relative C11b/C40/C54 energies are similar in magnitude to those obtained in previous studies of L12/D022/D023 competition in transition-metal aluminides.1,2 Calculations of the C49/C54 energetic competition are inaccurate; the differences in atomic coordination in these two structures are probably too large for the computational method to handle accurately. The total-energy results are interpreted by a detailed analysis of the electronic density-of-states (DOS) distributions. The stable structures do not correlate as strongly with DOS effects in the vicinity of the Fermi level as in the aluminides.

Ab Initio Calculations of Structural Energetics of Transition-Metal Aluminides and Silicides

1990 ◽  
Vol 213 ◽  
Author(s):  
A. E. Carlsson ◽  
P. J. Meschter
Keyword(s):  
Transition Metal ◽  
Band Structure ◽  
Ab Initio Calculations ◽  
Fermi Level ◽  
Ab Initio ◽  
Density Of States ◽  
Band Structure Calculations ◽  
Total Energies ◽  
Metal Aluminides ◽  
Structure Calculations

ABSTRACTTotal energies of binary and ternary -metral trialminides in the L12DO22 Do23Structures and binary Transition- metal disilicides in the C1lb, C40, C54, and C49 structures have been obtained by ab initio band-structure calculations. In aluminides the tetragonal Do22 and Do23 structures are stabilized relative to cubic L12P and in silicides the hexagonal C40 structure is stabilized relative to orthorhombic C54 and tetragonal C11b relative to C40, as the transition-metal d-electron count increases. The observed easier stabilization of L12 in Ti(AI,Fe) 3 relative to Nb(AI,Fe)is justified by the calculations. Location of the Fermi level in a quasigap in the density of states distribution rationalizes the observed structural stabilities in aluminides but not in silicides.

Intrinsic Optical Absorption in Germanium

1964 ◽  
Vol 19 (5) ◽  
pp. 548-552
Author(s):  
Günther Harbeke
Keyword(s):  
Optical Absorption ◽  
Low Temperatures ◽  
Energy Difference ◽  
Direct Absorption ◽  
Band Structure Calculations ◽  
Bulk Single Crystals ◽  
Transmission Measurements ◽  
Absorption Constant ◽  
Valence Bands ◽  
Structure Calculations

The absorption constant of germanium beyond the first direct absorption edge has been determined up to energies of 2.5 eV by transmission measurements on very thin samples prepared from bulk single crystals. The results are discussed in terms of recent band structure calculations and previous reflection measurements. At low temperatures the observed structure gives evidence for exciton formation connected with direct transitions at a saddle point in the energy difference between conduction and valence bands.

Band theory of insulating transition-metal monoxides: Band-structure calculations

1984 ◽  
Vol 30 (8) ◽  
pp. 4734-4747 ◽  
Author(s):  
K. Terakura ◽  
T. Oguchi ◽  
A. R. Williams ◽  
J. Kübler
Keyword(s):  
Transition Metal ◽  
Band Structure ◽  
Band Theory ◽  
Band Structure Calculations ◽  
Structure Calculations

Magnetism in 4d Transition Metal–Ag(001) Sandwiches

1991 ◽  
Vol 231 ◽  
Author(s):  
Dennis P. Clougherty ◽  
M. E. Mchenry ◽  
J. M. Maclaren
Keyword(s):  
Transition Metal ◽  
Band Structure ◽  
Ground State ◽  
Fermi Energy ◽  
Band Structure Calculations ◽  
Spin Polarized ◽  
Densities Of States ◽  
Ferromagnetic Ground State ◽  
Sandwich Configuration ◽  
Structure Calculations

AbstractUsing ab-initio spin-polarized layer Korringa-Kohn-Rostoker (LKKR) band structure calculations, we investigated the possibility of having a stable ferromagnetic ground state in 4d transition metal (TM)–Ag(001) sandwiches (TM = Tc, Ru, Rh, and Pd). In contrast to recent calculations performed on systems with TM overlayers on Ag (001), we find that the TM sandwich configuration gives a paramagnetic ground state. While excellent agreement in general is obtained for the layer-projected densities of states (LDOS), the sandwich configuration lowers the densities of states at the Fermi energy (EF) in the case of Rh and Ru by a small amount which seemingly prevents the marginal ferromagnetic instability predicted by Eriksson et. al. (Phys. Rev. Lett. 66, 1350 (1991)) from occurring.

Electronic Structures of P-Type Doped CuInS2

1996 ◽  
Vol 426 ◽  
Author(s):  
T. Yamamoto ◽  
H. Katayama-Yoshida
Keyword(s):  
Electronic Structures ◽  
Electronic Band Structure ◽  
Spherical Wave ◽  
Material Design ◽  
Electronic Band ◽  
Design Considerations ◽  
Band Structure Calculations ◽  
P Type ◽  
Structure Calculations ◽  
Codoping Method

AbstractWe have studied the electronic structures of CuIn(S0.875X0.125)2 (X=B, C, N, Si or P) based on the ab-initio electronic band structure calculations using the augmented spherical wave (ASW) method. We have clarified that the physical characteristics of the p-type doped CuInS2 crystals are mainly determined by a change in the strength of interactions between Cu and S atoms. On the basis of the calculated results, we discussed the material design considerations, such as controlling the strength of resistivity for p-type doped CulnS2 materials and converting the conduction type, from n-type to p-type by a codoping method.

LMTO Band Structure Calculations of ThCr2Si2-Type Transition Metal Compounds

1997 ◽  
Vol 130 (2) ◽  
pp. 254-265 ◽  
Author(s):  
Dirk Johrendt ◽  
Claudia Felser ◽  
Ove Jepsen ◽  
Ole Krogh Andersen ◽  
Albrecht Mewis ◽  
...  
Keyword(s):  
Transition Metal ◽  
Band Structure ◽  
Transition Metal Compounds ◽  
Metal Compounds ◽  
Type Transition ◽  
Band Structure Calculations ◽  
Structure Calculations

Relative stability of LI2, DO22, and DO23 structures in MAl3 compounds

1989 ◽  
Vol 4 (5) ◽  
pp. 1060-1063 ◽  
Author(s):  
A. E. Carlsson ◽  
P. J. Meschter
Keyword(s):  
Crystal Structure ◽  
Transition Metal ◽  
Energy Difference ◽  
Group Iv ◽  
Group V ◽  
Group Iii ◽  
Densities Of States ◽  
Electronic Densities ◽  
The Stability ◽  
The One

The structural energy differences between cubic LI2 and tetragonal DO22 crystal structures are calculated for MAl3 compounds, where M is a group III, IV, or V transition metal. The stability of the DO22 structure relative to L12 increases rapidly as the transition-metal d-electron count increases. Typical values of E(DO22) – E(L12) are 0.1–0.15 eV/atom (9600–14500 J/g-atom) for group III,  0.05 eV/atom ( 4800 J/g-atom) for group IV, and ∼ –0.2 eV/atom (∼ –19000 J/g-atom) for group V trialuminides. Similar trends are calculated for the DO23/L12 energy difference. The calculated electronic densities of states (DOS) show that each structure has a minimum in the DOS distribution at a characteristic d-electron count. The preferred crystal structure for a given compound is the one in which the Fermi level lies in the minimum.

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