Gömülü atom metodu ile sıvı HCP nadir toprak metallerinin atomlararası etkileşme potansiyelleri, sıvı yapıları ve bazı termodinamik özellikleri
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Dosyalar
Tarih
2005
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Yayıncı
Trakya Üniversitesi Fen Bilimleri Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu çalismada, sivi hcp nadir toprak geçis metallerinin yapisal ve termodinamik özelliklerini dogru olarak açiklayabilen atomlar arasi etkin çiftler potansiyellerinin, Gömülü Atom Metodu (GAM) ile elde edilmesi amaçlanmistir. Bu amaçla literatürde hcp geçis metalleri için kati özellikleri fit edilerek parametrize edilen farkli Gömülü Atom Metodlari ele alinmis, Zhang-Quyang Gömülü Atom Metodu (ZQ-GAM), Hu- Xu, Hu-Zhang, Hu-Deng'in Analitik Yeniden Düzenlenmis Gömülü Atom Metodlari (AYDGAM) ve Chen-Xu GAM ile çalisilmistir. S. S. Dalgiç vd. tarafindan fcc sivi geçis metallerinin Gömülü Atom Metodu hesaplamalari için önerilmis olan parametrizasyon metodu hcp yapisindaki bazi nadir toprak metalleri, Pr, Nd, Gd, Tb, Dy, Ho, Er ile hcp geçis metallerinden Be, Mg, Sc, Y, La, Ti, Zr, Co' a da uygulanmistir. ZQ-GAM, Hu-Xu AYDGAM, Hu-Zhang AYDGAM, Hu-Deng AYDGAM ve Chen-Xu GAM potansiyel fonksiyonlari önerilen parametrizasyon metodu kullanilarak hesaplanmistir. Ayrica Gömülü Atom Metodunda Finnis-Sinclair (FS) Efektif Çiftler Potansiyel Yaklasimi kullanilarak, ilk kez AYDGAM metodlari için FS yaklasimi gelistirilmis, enerji düzeltme terimlerinin de yer aldigi iki farkli FS efektif potansiyel metodu ile çalisilmistir. Hesaplanan Atomlar - arasi etkin çiftler potansiyelleri, sivi yapi teorilerinden Varyasyonel Hypernetted Chain (VMHNC)'nin giris datasi olarak kullanilmis, incelenen sistemlerin ergime noktalari civarindaki statik yapi faktörleri S(q) ve çiftler dagilim fonksiyonlari g(r) hesaplanarak deneysel sonuçlar ile karsilastirilmistir. Elde edilen yapisal özellikler ile sivi hcp geçis metallerinin iç enerji, Helmholtz serbestlik enerjisi ve entropileri hesaplanmis deneysel veriler ile karsilastirilmistir.
In the present work, the interatomic effective pair potentials which are capable of predicting both the structural and thermodynamic properties of the liquid hcp rare- earth metals have been obtained using the embedded atom method (EAM). For this purpose, the different versions of EAM model for the hcp metals which were parameterised by fitting the solid state properties in the literature have been taken into account. It has been studied with the Zhang-Quyang embedded atom method (ZQ- EAM), the Analytical Modified Embedded Atom Method (AMEAM) of Hu-Xu, Hu- Zhang, Hu-Deng and Chen-Xu EAM method. The parameterisation method proposed by S.S. Dalgic and co-workers for the EAM calculations of fcc liquid metals has been applied to hcp rare-earth metals such as Pr, Nd, Gd, Tb, Dy, Ho, Er and some hcp transition metals such as Be, Mg, Sc, Y, La, Ti, Zr, Co. The potential functions of the EAM models have been computed with this proposed parameterisation method. On the other hand, the Finnis-Sinclair (FS) effective pair potential approach in the EAM has been used and extended to AMEAM calculations for the first time in the literature. It has been studied with the two different FS approaches which include the energy correction terms of AMEAM. The interatomic effective pair interaction potentials are used as input data for the variational modified hypernetted chain (VMHNC) integral equation approximation which is one of the liquid state theories. The static structure factors and the pair distributions of the investigated systems at near their melting points are computed and compared with the experimental data. The computed structural properties have been used in order to obtain the thermodynamic properties of the liquid hcp metals such as internal energy, Helmholtz free energy, entropy and compared with experimental data and the theoretical results those obtained by others.
In the present work, the interatomic effective pair potentials which are capable of predicting both the structural and thermodynamic properties of the liquid hcp rare- earth metals have been obtained using the embedded atom method (EAM). For this purpose, the different versions of EAM model for the hcp metals which were parameterised by fitting the solid state properties in the literature have been taken into account. It has been studied with the Zhang-Quyang embedded atom method (ZQ- EAM), the Analytical Modified Embedded Atom Method (AMEAM) of Hu-Xu, Hu- Zhang, Hu-Deng and Chen-Xu EAM method. The parameterisation method proposed by S.S. Dalgic and co-workers for the EAM calculations of fcc liquid metals has been applied to hcp rare-earth metals such as Pr, Nd, Gd, Tb, Dy, Ho, Er and some hcp transition metals such as Be, Mg, Sc, Y, La, Ti, Zr, Co. The potential functions of the EAM models have been computed with this proposed parameterisation method. On the other hand, the Finnis-Sinclair (FS) effective pair potential approach in the EAM has been used and extended to AMEAM calculations for the first time in the literature. It has been studied with the two different FS approaches which include the energy correction terms of AMEAM. The interatomic effective pair interaction potentials are used as input data for the variational modified hypernetted chain (VMHNC) integral equation approximation which is one of the liquid state theories. The static structure factors and the pair distributions of the investigated systems at near their melting points are computed and compared with the experimental data. The computed structural properties have been used in order to obtain the thermodynamic properties of the liquid hcp metals such as internal energy, Helmholtz free energy, entropy and compared with experimental data and the theoretical results those obtained by others.
