(111)应变对正交相Ca_2P_(0.25)Si_(0.75)能带结构及光学性质影响的理论研究

The effect of the(111) strained on the band structure and optical properties of orthorhombic Ca_2P_(0.25)Si_(0.75) in the theoretical study

采用第一性原理平面波贋势方法对（111）应变下正交相Ca2P0.25Si0.75的能带结构及光学性质进行模拟计算.计算结果表明：（111）面在晶格发生100%-104%张应变时,带隙随着应变增加而增大;在晶格发生104%-112%压应变时,带隙随着张应变的增加而减小;88%-100%压应变时,带隙随着压应变的增加而减小;当压应变达到88%后转变为导体.当施加应变后光学性质发生显著的变化,随着压应变的增加静态介电常数、折射率逐渐减小,张应变则反之.施加压应变反射向高能方向偏移,施加张应变反射向低能方向偏移.施压应变吸收谱增大,施加张应变吸收谱变小.综上所述,应变可以改变Ca2P0.25Si0.75的电子结构和光学常数,是调节Ca2P0.25Si0.75光电传输性能的有效手段.

Energy band structure and optical properties of the orthorhombic Ca2P0.25Si0.75 with（111）strained have been calculated by the first-principle pseudo-potential method based on density functional theory（DFT）.The results show that orthorhombic Ca2P0.25Si0.75 is direct semiconductor and the band gap value increased with increasing of the tensile in the range of 100% -104%,but it is decreased with increasing of strain in the range of 104%-120% and in the range of 88%-100%.The orthorhombic Ca2P0.25Si0.75 is turned to metal with exceeding of the strain 88%.The optical properties have a significant change by straining.The dielectric constant and the refractive index are decreased with increasing of strain,in contrast,for tensile strain.The refractivity is moved to the direction of high energy with increasing of the compressive strain,is moved to the direction of low energy with increasing of the tensile strain.The absorption is increased with increasing of the compressive strain,while it decreased with increasing of tensile strain.In conclusion,straining is a useful method for modulating the photoelectric transmission property of the orthorhombic Ca2P0.25Si0.75.