Electronic, vibrational, superconducting and thermodynamic properties of cubic antiperovskite ZnNNi₃

Abstract

We present results of ab initio theoretical investigations of the structural and electronic properties of the cubic superconductor ZnNNi 3 by employing the plane wave pseudopotential method within the generalized gradient approximation. The density of states at the Fermi level is found to be governed by the Ni 3d electrons. A linear-response approach to the density functional theory is used to derive the phonon dispersion curves, vibrational density of states and the electronphonon coupling parameter. The calculated electron-phonon coupling constant λ and the logarithmically averaged phonon frequency are calculated to be 0.654 and 169.89 K, respectively, giving the superconducting transition temperature T C =2.925 K according to the Allen-Dynes formula. Our calculated value of T C is in excellent accord with the corresponding experimental value of 3 K. Using the phonon dispersion results, we further present an assessment of important thermodynamical properties such as internal energy (E), Helmholtz free energy (F), constant-volume specific heat (C V ), entropy (S) and Debye temperature ( ) in the framework of quasi harmonic approximation theory.

Phonon anomalies and superconductivity in the Heusler compound YPd2Sn

“…We have used the quasi-static approximation 32 to calculate the Debye temperature (H) of YPd 2 Sn. 33,34 The value of H is found to be 199 K, which is in an excellent agreement with the recent experimental value of 210 K in the work of Klimczuk et al 15 The electron-phonon coupling constant k also enters the electronic specific heat coefficient c, which is given as…”

Antiperovskites with Exceptional Functionalities

“…The cubic Ni 3 MgC represents an s‐wave BCS‐type type‐II superconductor, which gives a rare example similar to the noncuprate superconductor Ba 1− x K x BiO 3 for exploring the superconducting mechanism. Consequently, extensive experimental and theoretical investigations were carried out on Ni 3 MgC‐related superconductors, such as Ni 3 CuN, Ni 3 ZnN, Cr 3 GaN, and K 2 NiF 4 ‐type layered A 2 CNi 4 (A = Al, Ga, Sn) . The high Ni content in the crystal structure indicates that the magnetic interactions may play a crucial role in the emergence of superconductivity.…”

“…Consequently, extensive experimental and theoretical investigations were carried out on Ni 3 MgC-related superconductors, such as Ni 3 CuN, Ni 3 ZnN, Cr 3 GaN, and K 2 NiF 4 -type layered A 2 CNi 4 (A = Al, Ga, Sn). [97][98][99][100][101][102][103][104][105][106][107] The high Ni content in the crystal structure indicates that the magnetic interactions may play a crucial role in the emergence of superconductivity. Ni K-edge X-ray absorption and 13 C NMR measurements and theoretical computational simulations were performed to reveal the contributions of the local structure, electronic states, and electron-phonon interactions to the superconductivity.…”

Exact factorization-based density functional theory of electron-phonon systems

“…Since E BO [n U ] can be converted into an orbital-dependent functional by substituting n U = nk f nk |ψ nk | 2 , our approximation E geo [ψ nk ] implies an approximation for E[ψ nk ] = E BO [ψ nk ] + E geo [ψ nk ] and, in turn, the total energy in Eq. (48). The stationary conditions with respect to ψ * nk (r) lead to a nonadiabatic and nonlocal generalized KS potential of the form:…”

“…The electronic band structure, phonon modes and electron-phonon coupling terms define a BO reference state that contains enough information to evaluate several observables, such as the electron-phonon coupling constant λ and transition temperature T c in conventional superconductors such as MgB 2 , 6-22 electronic band structure renormalization, [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] and electronic mass enhancement and specific heat. 12,13,18,[41][42][43][44][45][46][47][48][49][50][51][52][53][54] Nevertheless, there is growing interest in capturing nonadiabatic electronphonon effects [55][56][57][58][59][60][61][62][63][64][65][66] by ab initio approaches that ...…”