بررسي ويژگي‌هاي ساختاري و اپتيكي تركيب MgAl2O4با استفاده از نظريۀ تابعي چگالي

Investigation of structural and optical propertie of MgAl2O4 using density functional theory

در اﯾﻦ ﻣﻘﺎﻟﻪ ﺳﺎﺧﺘﺎر اﻟﮑﺘﺮوﻧﯽ، ﺧﻮاص ﺳﺎﺧﺘﺎري از ﺟﻤﻠﻪ ﺛﺎﺑﺖ ﺷﺒﮑﻪ، ﻣﺪول ﺣﺠﻤﯽ، ﺗﺮاﮐﻢﭘﺬﯾﺮي، ﭼﮕﺎﻟﯽ و ﺧﻮاص اﭘﺘﯿﮑﯽ اﮐ ﺴﯿﺪ ا ﺳﭙﯿﻨﻞ )MgAl2O4( ﺑﺮرﺳـﯽ ﻣﯽﺷـﻮد. ﻣﺤﺎﺳـﺒﻪﻫﺎ ﺑﺎ اﺳـﺘﻔﺎده از روش اﻣﻮاج ﺗﺨﺖ ﺗﻘﻮﯾﺖﺷـﺪة ﺧﻄﯽ ﺑﺎ ﭘﺘﺎﻧﺴـﯿﻞ ﮐﺎﻣﻞ )FP-LAPW( در ﭼﺎرﭼﻮب ﻧﻈﺮﯾﮥ ﺗﺎﺑﻌﯽ ﭼﮕﺎﻟﯽ و ﺑﺎ ا ﺳﺘﻔﺎده از ﻧﺮماﻓﺰار WIEN2k ﺻﻮرت ﮔﺮﻓﺘﻪ ا ﺳﺖ. ﭘﺎراﻣﺘﺮﻫﺎي ﺳﺎﺧﺘﺎري و ﮔﺎف ﻧﻮاري ﺑﺎ ﺗﻘﺮﯾﺐﻫﺎي ﻣﺨﺘﻠﻒ ﺑﺮر ﺳﯽ ﺷﺪه اﺳﺖ و ﻧﺘﺎﯾﺞ ﭘﺎراﻣﺘﺮﻫﺎي ﺳﺎﺧﺘﺎري در ﺗﻘﺮﯾﺐ GGA-WC ﻧﺘﺎﯾﺞ ﮔﺎف ﻧﻮاري در ﺗﻘﺮﯾﺐ LDA ﺑﺎ ﻧﺘﺎﯾﺞ ﺗﺠﺮﺑﯽ ﺳﺎزﮔﺎري ﺑﻬﺘﺮي داﺷﺘﻪ ﻟﺬا در اداﻣﻪ روش MBJ ﺑﻪ ﻫﻤﺮاه دو ﺗﻘﺮﯾﺐ ذﮐﺮ ﺷﺪه ﺑﻪ ﮐﺎر ﮔﺮﻓﺘﻪ ﺷﺪه اﺳﺖ. ﮔﺎف ﻧﻮاري ﺑﺎ اﺳﺘﻔﺎده ازﺗﻘﺮﯾﺐ GGA-WC ﺗﻄﺎﺑﻖ ﺑﻬﺘﺮي ﺑﺎ ﺗﺠﺮﺑﻪ داﺷـﺖ ﺑﻨﺎﺑﺮاﯾﻦ ﺑﺮرﺳـﯽ ﺳـﯿﺴـﺘﻢ ﺗﺤﺖ ﻓﺸـﺎر ﺑﺎ اﺳـﺘﻔﺎده از ﺗﻘﺮﯾﺐ )MBJ+GGA(WC اﻧﺠﺎم ﮔﺮﻓﺖ. ﺧﻮاص اﭘﺘﯿﮑﯽ ﻧﻈﯿﺮ ﺗﺎﺑﻊ دياﻟﮑﺘﺮﯾﮏ، ﺿﺮﯾﺐﺷﮑﺴﺖ، ﺿﺮﯾﺐﺧﺎﻣﻮﺷﯽ، ﺗﺎﺑﻊ اﺗﻼفاﻧﺮژي، ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. ﻧﺘﺎﯾﺞ ﺑﻪ دﺳﺖ آﻣﺪه از ﺳﺎﺧﺘﺎر ﻧﻮاري ﻧﺸﺎن ﻣﯽدﻫﻨﺪ ﮐﻪ اﯾﻦ ﺗﺮﮐﯿﺐ ﻋﺎﯾﻖ ا ﺳﺖ و ﮔﺎف ﻧﻮاري 7/67 اﻟﮑﺘﺮونوﻟﺖ دارد. ﺿﺮﯾﺐ ﺷﮑ ﺴﺖ 1/55 ﻣﺤﺎ ﺳﺒﻪ ﺷﺪ. ﻧﺘﺎﯾﺞ ﻣﺤﺎ ﺳﺒﻪ ﺷﺪه در ﺗﻮاﻓﻖ ﺧﻮﺑﯽ ﺑﺎ ﻧﺘﺎﯾﺞ ﻧﻈﺮي و ﺗﺠﺮﺑﯽ دﯾﮕﺮان اﺳﺖ.

In this article, the electronic and structural properties of MgAl2O4 such as lattice constant, bulk modulus, compressibility, density; and optical propertieshave been investigated . Calculations were performed using the Full-Potential-Linearized Argument Plane Wave (FP-LAPW) method in the density functional theory framework by Wien2k code. Structural properties and band gap have been studied with different approximations. Compared to experimental results,the results of structural properties withGGA-WCapproximation and the results of band gap withLDA approximation have been better compatibility, therefor; the MBJ method along with two mentioned approximations has been used later. The effect of pressure on MgAl2O4 have been investigated withMBJ+GGA(WC)approximation. The optical properties such as dielectric function, refraction index, extinction coefficient and energyloss function have been studied. The obtained results from band structure shows that MgAl2O4is an insulator and the band gap is equal to 7.67 eV. Therefraction indexis equal to 1.55. The obtained results have been in good agreement with other theory and experimental results.