Phonon and thermal expansion properties in Weyl semimetals MX (M = Nb, Ta; X = P, As): ab initio studies.

Weyl semimetal (WSM) is a new type of topological quantum material for future spintronic devices. Using the first-principles density functional theory, we systematically investigated the thermal expansion properties, and the temperature dependence of isovolume heat capacity and bulk modulus in WSMs MX (M = Nb, Ta; X = P, As). We also presented the phonon dispersion curves and its variation under stress in MX and the anisotropic thermal expansion properties due to the anisotropic crystal structure in WSMs have been predicted in our calculations. Intriguing, we found that the heat capacities increase more rapidly with increasing temperature in the low temperature region for all MX. Furthermore, our results showed that the thermal expansion properties are determined mainly by the isovolume heat capacity at low temperatures, while the bulk modulus has the major effect at high temperatures. These results are useful for applications of WSMs in electronic and spintronic devices.

Electronic and optical properties of quaternary alloy GaAsBiN lattice-matched to GaAs.

Employing first-principles combined with hybrid functional calculations, the electronic and optical properties of GaAs alloyed with isovalent impurities Bi and N are investigated. As GaAsBiN alloy is a quaternary alloy, the band gap and the lattice constant of the alloy can be individually tuned. Both impurities are important to the valence band and conduction band of the alloy, with the band gap of the alloy being dramatically reduced by Bi 6p states and N localized 2s states. Interestingly, the calculated optical properties of the quaternary alloy are similar to those of undoped GaAs except that the absorption edge has a redshift toward lower energy. These results suggest potential interest in the long-wavelength applications of GaAsBiN alloy.

[Analysis of surface enhanced Raman scattering spectra of oxyhemoglobin for liver cancer with combined multivariate statistics].

Investigation of surface-enhanced Raman spectra of oxyhemoglobin for 30 liver cancers and 30 normal persons based on the silver nanofilm was reported. Principal components analysis (PCA) and independent variable T test were employed to develop effective diagnostic algorithms for distinguishing liver cancer form normal. Discriminant analysis was used to evaluate the diagnostic efficiency and the result indicates that SERS spectra of the oxyhemoglobin are obviously different between normal persons and liver cancers. PCA and independent variable T test were employed to get a three-dimensional scatter plot of PC scores for the healthy and cancer groups, and it can be learned that they are distributed in separate areas. By using the method of discriminate analysis, it was fount that the diagnostic algorithm separates the two groups with sensitivity of 96.7% and diagnostic specificity of 90%, the overall diagnostic accuracy was 93.3%. By analyzing the assignations of the SERS bands, it was found that the content of asparagine, tyrosine and phenylalanine in the hemoglobin are significantly lower than healthy people. The results from this exploratory study demonstrate that SERS detection of oxyhemoglobin for liver cancers based on the method of PCA combined with independent variable T test is expected to develop into a new type of liver cancer diagnostic tool.