5014

4718

كارشناسي ارشد

فيزيك

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1388

هفت، 70ص:مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

جواد هاشمي فر

هادي اكبر زاده

21/11/88

پرويز كاملي، مجتبي اعلايي

فيزيك

ID4718

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

Ab initio study of the structural properties of bulk MnSe and cubic MnSe 001 nanowires Mohammad Haassan Amiri amiri mhs@gmail com 1388 3 23 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Dr S J Hashemifar Supervisor jhashemifar@gmail comAbstractWe employed pseudo potential and full potential methods to study the structural electronic and magnetic propertiesof bulk MnSe by using two software WIEN2k and PWscf MnSe has 3 structural phases NaCl Zinc Blende andhexagonal NiAs We considered both ferromagnetic and antiferroma gnetic phases in our calculations Experimental results indicate that NaCl phase with type II magnetic ordering NaCl 111 is the most stable phasewhile our calculation with PWscf and GGA exchange correlation energy showed the hexagonal phase has the lowestenergy Then we applied WIEN2k and different exchange correlation energies GGA LSDA and LDA U to ourcalculation to solve this inconsistency we got the best result within LDA U method confirming the stability ofMnSe in NaCl structure and type II antiferromagnetic state The calculated energy gap within LDA U 2eV isalso very close to the experimental result Therefore LDA U seems a reliable method for studying structural andelectronic properties of MnSe After bulk calculations we studied structural properties of square cross sectionalMnSe nanowire by using PWscf software and applying PBE GGA exchange correlation functional We calculatedthe first 4 diameters of this nanowire and after full atomic relaxation obtained their cohesive energies Thesecalculations showed that antiferromagnetic is the stable phase for all 4 diameters The Young s modulus of the firstand second diameter nanowires was calculated and found to be larger than bulk value We used twophenomenological model macroscopic and microscopic models to study and understand the behavior of thecohesive energies In the first model the concept of dangling bond energies was used to analyze the nanowirecohesive energies while in the second model surface and edge energy parameters were introduced for macroscopicenergy description of MnSe nanowires Keywordspseudo potential full potential structural phase exchange correlation energy nanowire Young s modulus dangling bond cohesive energy

جواد هاشمي فر

هادي اكبر زاده

پرويز كاملي، مجتبي اعلايي