The compressibilities of liquid Sn-Tl, In-Bi, Sn-ln, Bi-Sb, and Bi-Cd-Tl alloys
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data on the p h y s i c a l p r o p e r t i e s of liquid m e t a l s and alloys is n e e d e d in a n u m b e r of p r a c t i c a l a p p l i c a t i o n s . The c a l c u l a t i o n of p h y s i c a l p r o p e r t i e s f r o m i n t e r a t o m i c p o t e n t i a l s is t h e o r e t i c a l l y p o s s i b l e by u s i n g a set of e q u a t i o n s obtained a f t e r a d m i t t i n g the v a l i d i t y of the p a i r i n t e r a c t i o n a p p r o x i m a t i o n , x One then c o n s i d e r s m e t a l l i c liquids as being m i x t u r e s of n e u t r a l p s e u d o - a t o m s c o m p o s e d of s c r e e n e d m e t a l l i c i o n s . A p p r o x i m a t i o n s i n t r o d u c e d for the c a l c u l a t i o n (for i n s t a n c e the P e r c u s - Y e v i c k equation) and the p r e s e n c e of s e v e r a l a r b i t r a r y c o n s t a n t s d e p r i v e this m e t h o d of s o m e p r a c t i c a l i n t e r e s t except for the p u r pose of v e r i f i c a t i o n of the f u n d a m e n t a l h y p o t h e s e s .2,3 To a c h i e v e a c t u a l c a l c u l a t i o n s of p h y s i c a l p r o p e r t i e s , a s e m i e m p i r i c a l ~ m o d e l of m e t a l l i c liquids b a s e d on the m o r e g e n e r a l l y a d m i t t e d hypotheses on t h e i r s t r u c t u r e had t h e r e f o r e to be d e v i s e d , t'4 The a i m of the p r e s e n t study is to a t t e m p t to c a l c u late the d e n s i t i e s , v e l o c i t i e s of u l t r a s o n i c w a v e s , and coefficients of s e l f - d i f f u s i o n in l o w - m e l t i n g liquid m e t a l s and a l l o y s . The m o d e l used for this p u r p o s e is t e s t e d by m e a n s of m e a s u r e m e n t s of the i s o t h e r m a l c o m p r e s s i b i l i t i e s in s e v e r a l l o w - m e l t i n g m e t a l s and a l l o y s and of data f r o m the l i t e r a t u r e on X - r a y d i f f r a c tion 5'~ and s e l f - d i f f u s i o n .8-x~
into e l e c t r i c p u l s e s and shown on the s c r e e n of a T e k t r o n i x o s c i l l o s c o p e , allowing the t i m e of t r a v e l through the liquid to be m e a s u r e d a c c u r a t e l y . A l l m e a s u r e m e n t s were c a r r i e d out in an a r g o n a t m o s p h e r e . The t e m p e r a t u r e of the liquid m e t a l was r e g u l a t e d and u n i f o r m to I~ at 500~ The a s s e m b l y a n d the a l l o y s used for t h e s e e x p e r i m e n t s w e r e the s a m e as in Ref. 12. The p r e s e n c e of tiny gas b u b b l e s on the i n t e r f a c e s tended to r e d u c e g r e a t l y the a m p l i t u d e of the echos. This p h e n o m e n o n was r e d u c e d to a r e a s o n a b l e side effect by m e l t i n g the alloy in an a u x i l i a r y f u r n a c e and c a s t i n g it in the g r a p h i t e c r u c i b l e in a p r i m a r y v a c u u m . The o v e r a l l p r e c i s i o n of the v e l o c i t y m e a s u r e m e n t s is b e t t e r than 1 pct. C o r r e c t i o n has not been made for the t h e r m a l e x p
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