Use of computer simulation technique to study atomic migration in solids

Conference · Tue Oct 01 00:00:00 EDT 1985

OSTI ID:6308585

Vashishta, P

Nature of ionic motions in superionic conductors AgI and Ag/sub 2/S are studied using molecular-dynamics (MD) technique. Our model of these superionic conductors is based on the use of effective pair-potentials. To determine the constants in these potentials, cohesive energy and bulk modulus are used as input; in addition one uses notions of ionic size based on the known crystal structures. The ..alpha.. in equilibrium ..beta.. structural phase transition in AgI is studied with the use of the new molecular dynamics (NMD) technique which allows for a dynanical variation of the shape and size of the cell. In the present model, upon heating the ..beta..-AgI, the iodine ions undergo a hcp ..-->.. bcc transformation and silver ions become mobile, whereas the reverse transformation is observed on cooling of ..alpha..-AgI. The calculated ..alpha.. in equilibrium ..beta.. transition temperature, and structural and dynamical properties are in good agreement with experiments. It has also become possible to observe crystal growth of ..alpha.. and ..beta.. phases when a system of molten AgI is cooled to different temperatures. Transition temperatures determined from the studies of ..alpha.. in equilibrium ..beta.. structural transitions and from crystal growth studies are in good agreement. The calculated transition temperatures are also in good accord with the experimental results. A model of superionic conductor Ag/sub 2/S is also studied. The silver density map and its temperature dependence is calculated. We have also calculated the x-ray and neutron structure factors which explain the anomalous intensity at and near Q = (1.6, 1, 0) observed in diffuse scattering experiments. A study of low-energy excitations in Ag/sub 2/S is in progress.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 6308585
• Report Number(s): CONF-8510245-1; ON: DE86004200
• Resource Relation: Conference: International conference on solid state ionics, Lake Tahoe, CA, USA, 18 Oct 1985; Other Information: Paper copy only, copy does not permit microfiche production
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SILVER IODIDES
ATOM TRANSPORT
CORRELATION FUNCTIONS
CRYSTAL GROWTH
CRYSTAL-PHASE TRANSFORMATIONS
SILVER SULFIDES
MOLECULAR STRUCTURE
COMPUTERIZED SIMULATION
CRYSTAL STRUCTURE
IONIC CONDUCTIVITY
TRANSITION TEMPERATURE
CHALCOGENIDES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FUNCTIONS
HALIDES
HALOGEN COMPOUNDS
IODIDES
IODINE COMPOUNDS
NEUTRAL-PARTICLE TRANSPORT
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RADIATION TRANSPORT
SILVER COMPOUNDS
SIMULATION
SULFIDES
SULFUR COMPOUNDS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
360603* - Materials- Properties
656000 - Condensed Matter Physics