Calculated structural-dependent optical properties of alloys TiNi, TiPd, and TiPt

Abstract

Electronic structures and optical properties of martensitic alloys TiNi, TiPd, and TiPt in both the lowtemperature B19 (B19Ј in the case of TiNi͒ and the high-temperature B2 phases are systematically calculated using the flat-principles local density functional approach. Our results on TiNi B2 and B19Ј phases agree well with the existing experimental data where drastic changes of optical conductivity in the infrared region from B2 to B19Ј phase were observed. Our results show that optical matrix elements are important in understanding the optical properties of these alloys, especially in obtaining the correct peak intensities. Because of the different crystalline symmetry between the low-temperature B19 ͑B19Ј in the case of TiNi͒ phase and the high-temperature B2 phase, different polarization dependence in the optical conductivity of the two phases is expected. We present the polarization-dependent optical conductivities in these martensitic alloys.

The electronic, elastic, and structural properties of Ti–Pd intermetallics and associated hydrides from first principles calculations

“…We calculated the total energies and structural properties of several other competing phases [CrB (oC8, B33), AuCu (tP2, L10), NiTi (mP4, B19 0 )]. Although the calculated equilibrium lattice parameters are in good agreement with experiment [14] (Table 1) and with previous ab initio calculations [26][27][28], the ground-state structure found in our calculation actually is not the experimentally reported AuCd-type (B19) structure. More specifically, the formation energies of the AuCd-, AuCu-, CsCl-, and CrB-type structures are less stable by 1.0, 1.4, 8.0, and 13.3 kJ (mol of atoms) À1 than that of the NiTi-type structure.…”

“…More recently, Curtarolo et al calculated structural stabilities and enthalpies of formation for five intermetallics (Ti 3 Pd, Ti 2 Pd, TiPd, TiPd 2 , TiPd 3 ) using an ultrasoft pseudopotential within the local density approximation (LDA) [30]. They found that the energies of the L1 0 and B19 phases of TiPd are essentially degenerate, which is inconsistent with previous calculations [26][27][28].…”

“…These studies include the elastic constants of the B2 phase [25], the structural properties of the B2, B19, and B19 0 phases [26], the optical properties of the B2 phase [27], and the structural energies and phonon dispersion of the B2 phase [28]. More recently, Curtarolo et al calculated structural stabilities and enthalpies of formation for five intermetallics (Ti 3 Pd, Ti 2 Pd, TiPd, TiPd 2 , TiPd 3 ) using an ultrasoft pseudopotential within the local density approximation (LDA) [30].…”

Thermopower behavior for the shape memory alloy NiTi

“…The electronic band structure of NiTi alloys has been calculated, for example, by Kulkova et al 21 et al 22 The calculations for the martensitic phase typically yield the Fermi level situated slightly above a small peak in the density of states ͑DOS͒, which can lead to nonlinearity in the thermopower. To demonstrate this situation, we employ a simple DOS peak shown in the inset of Fig.…”

Electronic study of FeTi, CoTi, and NiTi alloys: bulk, surfaces, and interfaces

“…Additionally, NiTi exhibits the martensic transition from the austenic B2-phase (like CsCl-structure) to the monoclinic B19'-structure upon cooling, proceeded by the so-called premartensic phenomena with the martensic transformation temperature near room temperature (T M = 333 K) [5]. This compound being the basic industrial shape memory alloy (SMA) is under intensive study over the world [6][7][8][9][10][11][12][13][14]. Recent spectroscopic ellipsometry study of FeTi, CoTi, and NiTi alloys has revealed strong optical transitions and has explained the similarities and the differences among optical conductivity (OC) spectra and the measured results are much closer to those obtained from LAPW method [15].…”