PHONON DISPERSION AND THERMOPHYSICAL PROPERTIES OF SODIUM

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PHONON DISPERSION AND THERMOPHYSICAL

PROPERTIES OF SODIUM

O. Gupta

To cite this version:

JOURNAL DE PHYSIQUE

CoZZoque C 6 , suppZ6ment au n o 12, Tome 42, d6centbre 1982 page C6-380

PHONON DISPERSION AND THERMOPHYSICAL PROPERTIES OF SODIUM

O.P. Gupta

Physics Department, J . Christian CoZZege, AZZahabad, India.

A h s t r a c t

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An e q u i l i b r i urn c o n d i t i o n , w h i c h p r e s e r v e s t h e c r y s t a l

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s t a b i l i t y , is d e r i v e d . T h i s c o n d i t i o n i n c o n j u n c t i o n w i t h r e c e n t d y n a m i c a l model i s employed t o s t u d y t h e phonon d i s p e r s i o n a n d t h s r m o p h y s i c a l p r o p e r t i e s o f h'a. T h e t h e o r e t i c a l r e s u l t s are i n g o o d a g r e e m e n t w i t h t h e e x p e r i m e n t a l v a l u e s . 1.

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c o n s t a n t s i n t e r m s o f e l a s t i c c o n s t a n t s Ci and o n e ZB f r e q u e n c y . 3 . N u m e r i c a l Computation.- E x p e r i m e n t a l v a l u e s o f C a n d o t h e r p a r a - i j meters a t 90 K u s e d i n c a l c u l a t i o n s a r e : Cll= 0.808, C12= 0 . 6 6 4 , Cs4= 0.586 ( a l l i n u n i t s of l o l 1 d y n

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d y n an-'). The. phonon d i s p e r s i o n , l a t t i c e s p e c i f i c h e a t , and DW f a c t o r a r e c a l c u l a t e d a s u s u a l [15]

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W e d i s p l a y o u r t h e o r e t i c a l r e s u l t s f o r phonon d i s p e r s i o n a l o n q w i t h t h e e x p e r i m e n t a l v a l u e s [17] i n F i g . 1. The a g r e e m e n t b e t w e e n t h e o r y a n d e x p e r i m e n t i s v e r y g o o d - L a t t i c e s p e c i f i c - PeES6NT CALCULI\IION EXPERIMENTAL Poll-5 0

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c u r v e s i s s i m i l a r i n s p i t e o f t h e f a c t t h a t t h e m e a s u r e d v a l u e s a r e n o t v e r y c o n c o r d a n t w i t h o n e a n o t h e r . I t i s d i s c o n c e r t i n g t o f i n d t h a t how 0.4- much t h e t h e o r e t i c a l r e s u l t s d e v i a t e f r o m t h e e x p e r i m e n t a l p o i n t s d u e 0 :152.51(

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/ 3 . T h e p r e s e n t s t u d y d e m o n s t r a t e s t h a t t h e s i m 2 l e model p m v i d e s a g o o d o v e r a l l u n d e r s t a n d i n g o f phonon d i s p e r s i o n a n d t h e m o p h y s i c a l p r o p e r t i e s of Na. _{R e f e r e n c e s}

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a n 3 Hemkar,W . P . , Z.Phys.Chem -801 i d s

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