In this work, the elastic anisotropy, mechanical stability, and electronic properties for P42/mnm XN (XN = BN, AlN, GaN, and InN) and Pbca XN are researched based on density functional theory. Here, the XN in the P42/mnm and Pbca phases have a mechanic stability and dynamic stability. Compared with the Pnma phase and Pm-3n phase, the P42/mnm and Pbca phases have greater values of bulk modulus and shear modulus. The ratio of the bulk modulus (B), shear modulus (G), and Poisson's ratio (v) of XN in the P42/mnm and Pbca phases are smaller than those for Pnma XN and Pm-3n XN, and larger than those for c-XN, indicating that Pnma XN and Pm-3n XN are more ductile than P42/mnm XN and Pbca XN, and that c-XN is more brittle than P42/mnm XN and Pbca XN. In addition, in the Pbca phases, XN can be considered a semiconductor material, while in the P42/mnm phase, GaN and InN have direct band-gap, and BN and AlN are indirect wide band gap materials. The novel III-V nitride polymorphs in the P42/mnm and Pbca phases may have great potential for application in visible light detectors, ultraviolet detectors, infrared detectors, and light-emitting diodes.

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Abstract

Aiming at the problem of scarcity in traditional tracking algorithms in order to track behavior more rapidly and accurately, a behavior tracking algorithm based on linear discriminant analysis combined with the gradient vector flow is presented. First, the gradient vector flow is calculated in the reference coordinate system, the appropriate curve parameters are set, and the position of the behavior is determined. Then, the discreteness is calculated within the range of behavior, the discriminant function is defined, and the maximum value and the best eigenvector are obtained. Last, the behavior is detected when the value of the dispersion degree is less than the set threshold. The new algorithm is not affected by background changes. Compared with existing algorithms, the simulation results show that the method is easy to realize and has a more stable tracking effect.