The force constants of germanium

164

LATTICE

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CONFERENCE

A C O M P A R I S O N OF T H E T H E R M O D Y N A M I C F.CoC. AND H.C.P. LATTICES C. I s e n b e r g a n d C. D o m b London, W.C.2, England) By

suitable

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to

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central

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temperature

by

polymorphic

A20.

the

specific

and

transition

VIBRATION

THE

FORCE

The developed, its

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into

out

with

T o be

published

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their

become

on l a t t i c e s the

method

nearest

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the

advance

properties

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thermodynamic

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of

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observed

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(PERICLASE) 9

Military

College

Theory

account

given

wave

constants.

and

helium

moments

6

C.C.R.

Reactor

Physics

OF G E R M A N I U M

to the

are

and

paper

with

1 No.

OF T H E

recently

continuation

J o u a n i n I0 ( E u r a t o m (Varese) Italy)

Karman

taking

constants,

normal

9.

Born-yon

neighbours

force

(Royal

heats

this

low

compared

solid

OF MO g

CONSTANTS

N . K . P o p e II Canada)

even the

a considerable

Domb, in

in

of a n a l y t i c

accurately

J. P e r e t t i a n d Ch. Department, Ispra,

A21.

term

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moments

models

Vol.

King's

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method

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AND

Laboratory,

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TITLES

PROPERTIES

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interactions.

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molecular

F°C.C.

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ABSTRACTS

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of C a n a d a ,

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frequencies

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eigenvectors

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elsewhere.

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University

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of Montpellier,

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Vol.

1 No.

stants that in

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and measured

it

and

possibly It

constants

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dynamical certain

directions. constants terms

not

in

AND

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only

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165

directions

interactions

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found

TITLES

symmetry

fifth-neighbour

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in reciprocal

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of the

curves

data.

combinations

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ABSTRACTS

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shows account

values

for

interactions

others. that

matrix

take

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were

three shown

linear

Fourier

to

to r e p r e s e n t

force

CONFERENCE

dispersion

is n e c e s s a r y

order

the

is

LATTICE

all

c a n be

Fourier

space

of the the

linearly

obtained

are

also

complete

c a n be

of the

from

data

Certain

derived.

given

present

analysing

symmetry

combinations

are

such

o f the

Fourier

i n the

necessary

The

to d e t e r m i n e

by

curves

independent

this

elements

obtained

dispersion

coefficients.

coefficients sufficiently

components

of force

directly

in

conditions

on the

experimental

a set

of F o u r i e r

data co-

efficients.

A22.

SHELL AND S O L I D S 12

EXCHANGE

B.G.

(University

Dick

Recently forces

model.

of This

foundations and

models

and

covalent

these

review along

lattice been

proposed

A23.

APPLICABILITY M.H. Brodsky for Research Philadelphia

dynamic electron

"shell

effective

Work supported

13.

Supported

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TO THE

a n d E. B u r e t e i n (Department on the S t r u c t u r e o f M a t t e r , 4, P e n n s y l v a n i a )

part

City,

charge

have

INTERACTIONS

the

simpler

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and

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crystals

MODELS

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U.S.

Science Atomic

VIBRATIONS

of P h y e i Q s University

successfully

experimental

National the

LATTICE

having

used ions

values

and Laboratory of Pennsylvania,

to c a l c u l a t e with

closed

of e + a r e

Foundation. Energy

OF L i H 13

Commission.

the shell

obtained