مقایسۀ تأثیر شکل هندسی و سطح مقطع ذرات میله ای شکل در تشکیل فاز دو محوره و هومئوتروپیک

نوع مقاله : مقاله پژوهشی کامل

نویسندگان

1 گروه فیزیک، دانشکده علوم، دانشگاه شهید چمران اهواز، اهواز، ایران

2 گروه فیزیک، دانشکده علوم، دانشگاه فسا،فسا، ایران

چکیده

در این مقاله به بررسی تأثیر شکل هندسی ذرات بر گذارفاز تک محوره-دو محوره و نماتیک پلنار-هومئوتروپیک برای ذرات استوانه ای شکل سخت ومیله های مکعب مستطیلی سخت بین دودیوارۀ موازی می پردازیم. محاسبات با استفاده از نظریۀپارسونز-لیدر تقریب زوانزیگ انجام شده است. این ذرات یک گذار فاز مرتبۀ اول از فاز پلانار به هومئوتروپیک نشان دادند که این نوع گذار فاز برای هر دو نوع ذره در یک بحرانی خاتمه می‌یابد که برای ذرات مکعب مستطیل حدود و برای ذرات استوانه ای می باشد. هم چنین گذار فاز تک محوره به دو محوره نیز برای هر دو سامانه مشاهده می شود که با کاهش نسبت در چگالی‌های بالاتر رخ می‌دهد که علت آن کاهش مساحت ممنوعه با نظم پلنار است. این نوع گذار فاز پیوسته می‌باشد. محاسبات نشان می دهند که هر دو نوع گذارفاز بررسی شده برای ذرات استوانه‌ای شکل در چگالی‌های پایین تر نسبت به ذرات مکعب مستطیل رخ می‌دهدکه این ناشی از تفاوت سطح ممنوعه و جذب بیشتر دیواره ها برای ذرات استوانه ای است.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Comparison of the effect of geometric shape and Cross-section of rod particles in biaxial and homeotropic phase formation

نویسندگان [English]

  • Sakine Mizani 1
  • Roohollah Aliabadi 2
  • ,Hamdollah Salehi 1
1 1Department of Physics, Faculty of Science, ShahidChamran University of Ahvaz, Ahvaz, Iran
2 2Department of Physics, Faculty of Science,Fasa University, Fasa, Iran
چکیده [English]

In this article we investigate the effects of particles’ geometry on the uniaxial-biaxial and planar nematic-homeotropic phase transition of hard cylinders and hard rectangular rods between two structureless walls. The calculations are doneusing the Parsons-Lee theory into the Zwanzig approximation. These particles show a first order phase transition from planar to homeotropic that disappears at a critical point for both particles which this critical point is and for hard rectangular and cylinder rods, respectively. In addition, there is a second order phase transition called uniaxial planar nematic to biaxial planar nematicwhere there is three different optical axes for both shapes. This transition occurs at higher densities for the particles with smaller shape anisiorpies due to decreasing of excluded area inplanar order. Our calculations depict that both types of phase transitions take place at lower densities

کلیدواژه‌ها [English]

  • uniaxial
  • biaxial
  • planar
  • homeotropic
  • Parsons-Lee

مراجع

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پژوهش سیستم های بس ذره ای
دوره 11، شماره 1 - شماره پیاپی 28
بهار1400
خرداد 1400
صفحه 56-67

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سابقه مقاله

  • تاریخ دریافت: 24 اردیبهشت 1398
  • تاریخ بازنگری: 27 مهر 1399
  • تاریخ پذیرش: 06 اردیبهشت 1400

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