Investigation on the Stability, Elastic Properties, and Electronic Structure of Mg₂Si Doped with Different Concentrations of Cu: A First‐Principles Calculation

Abstract

Herein, the effects of Cu doping with different concentrations on the stability, elastic properties, and electronic structure of Mg2Si are investigated by first‐principles calculations based on density functional theory. The research results show that Mg2Si and Mg8−xSi4−yCux+y (x, y) = {(0.125, 0), (0, 0.125), (0.25, 0), (0, 0.25), (0.5, 0), (0, 0.5), (1, 0), (0, 1)} are stable in the system. The Cu atoms tend to preoccupy Mg sites in Mg2Si lattices, and the alloying ability is stronger than that of Mg8Si4−yCuy (y = 0.125, 0.25, 0.5, 1). Although all dopants are brittle phases, the doping behavior of Cu atoms improves the elastic and plastic properties of the Mg2Si alloy system. The bonding modes of the crystal are also changed. The SiCu covalent bond formed by Mg8−xSi4Cux (x = 0.125, 0.25, 0.5, 1) further increases the structure stability. Meanwhile, Mg7Si4Cu and Mg8Si3Cu are changed from semiconducting to metallic state by energy band structure analysis. It not only increases the carrier concentration, but also reduces the free electron transition energy, which improves the conductivity of the intrinsic Mg2Si. These investigations will provide some theoretical basis for the application of Mg2Si intermetallic compounds in structural materials and thermoelectric materials.

First‐Principles Study on Electronic and Elastic Properties of Co, Ni, Cu, and Mo‐Doped Β‐Si3N4

“…The Voigt and Reuss models provide the upper and lower bounds of the effective modulus, respectively. The arithmetic average of the two models, known as the Voigt‐Ruess‐Hill approximation, [ 32 ] yields a more accurate estimate of the volume and shear moduli. Table 4 shows the calculated values of these moduli using the Voigt‐Ruess‐Hill approximation, as given by the following equations.…”

“…The OTFG ultrasoft [ 29 ] pseudopotential was used to describe the interaction between electrons and ions. The general gradient approximation (GGA+U) and Perdew‐Burke‐Ernzerhof (PBE) [ 32 ] methods were employed to estimate the exchange and correlation energies. Monkhorst‐Pack k‐point grid integration was used to integrate the Brillouin zone.…”

The Degradation Mechanism of Mg2Si during Exploitation at High Temperature

“…Based on the first‐principle calculation, [ 14,30 ] the interstitial Mg (I Mg ), interstitial O (I O ), and Mg vacancy (V Mg ) in the lattice of Mg 2 Si are the origins of n‐ and p‐type conduction of samples, that is, the I Mg acts as donor providing electrons, and I O and V Mg act as the acceptors providing holes. Therefore, the conduction type of the sample is the result of the carrier compensation between electrons and holes.…”

“…[ 10 ] The results of theoretical calculations showed that undoped Mg 2 Si crystals exhibit n‐type conduction, [ 11,12 ] which is mainly due to the presence of 4b vacancy in the lattice and the easy entry of Mg atoms to generate donor level, [ 10 ] i.e., interstitial Mg atom (I Mg ) leads to n‐type conduction and Mg vacancy (V Mg ) leads to p‐type conduction in Mg 2 Si lattice. [ 10,13,14 ] This means that decreasing I Mg or increasing V Mg during postannealing may cause the sample to become p‐type conduction. [ 15,16 ] Ogawa et al [ 17 ] reported that some of as‐deposited undoped Mg 2 Si films showed n‐type, and the others showed p‐type conduction at room temperature.…”

Magnetic Properties of 3d Transition Metal Atoms (V, Cr, Mn, Fe, Co, or Ni)‐Doped Mg2Si

“…[4,5] Mg 2 Si has been widely used in many fields due to its attractive properties such as thermoelectric, optoelectronic, electrochemical, and mechanical ones. To improve these properties, especially the thermoelectric property, different elements were doped into Mg 2 Si, such as Ag, [6] B, [7] Bi, [8,9] Cu, [10] Li, [11] P, [12] Sb, [13,14] Y, [15] rare earth elements, [16] and codoped strategy. [17,18] Undoped Mg 2 Si is well known as a nonmagnetic semiconductor.…”