مدهای فونونی نوری در بلور BaWO4

نوع مقاله: مقاله پژوهشی کامل

نویسندگان

1 دانشجوی دکتری فیزیک ماده چگال دانشگاه دامغان

2 دانشگاه علوم پایه دامغان

چکیده

با استفاده از نظریه تابعی چگالی اختلالی، بارهای مؤثر بورن، بسامدهای فونونی مرکز ناحیه بریلوئن و طیف بازتاب مادون قرمز در فرود عمود بر سطوح [100] و [001] برای بلور BaWO4 به‌دست آمده‌اند. اختلاف زیاد بارهای مؤثر بورن به‌دست آمده با بارهای یونی اسمی بیانگر پیوندهای شیمیایی با طبیعت یونی-کوالانسی آمیخته است. با استفاده از نظریه گروه و جدول مشخصه گروه نقطه‌ای C4h، مدهای فونونی برحسب گونه‌های تقارنی شناسایی شدند. بسامدهای فونونی به‌دست آمده تطابق خوبی را با مقادیر تجربی گزارش شده نشان می‌دهند. نتایج به‌دست آمده، بسامد یک مد فعال رامان از گونه تقارنی gB که به‌طور تجربی مشاهده نشده ‌است را پیش‌بینی می‌کنند.

کلیدواژه‌ها


عنوان مقاله [English]

Optical phonon modes in BaWO4 crystal

چکیده [English]

The Born effective charges, zone center phonon modes and infrared reflectivity spectra at normal incidence on the [100] and [001] surface of BaWO4 were calculated, using density functional perturbation theory. The calculated born effective charges display large deviations from nominal ionic charges, reflecting the mixed ionic-covalent nature of the chemical bonding. The phonon modes were identified in terms of symmetry species, using group theory and character table of C4h point group. The calculated phonon frequencies were in good agreement with the reported experimental values. The obtained results predict the frequency of a Raman active Bg mode that has not been earlier observed experimentally. 

کلیدواژه‌ها [English]

  • Density functional perturbation theory
  • Phonon frequencies
  • Barium tungstate
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