Molecular Dynamics Simulation Study of the Behavior of Molecular Crystal Tin Tetraiodide under Hydrostatic Pressure

The Journal of Chemical Physics

Sugiyama

Fujii

2000

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The pressure-temperature phase diagram of SnI 4 was investigated to examine the inherent instability of crystalline SnI 4 in terms of undergoing pressure-induced solid state amorphization, by conducting molecular dynamics simulations prior to studies involving laboratory experiments. The SnI 4 molecules are regarded as rigid tetrahedra interacting with one another via van der Waals forces. In order for the isothermal-isobaric ensemble to be achieved, the well-established Nosé -Klein scheme combined with the momentum scaling method was adopted when carrying out the simulations. The system was carefully heated up under fixed hydrostatic pressure from the low-pressure crystalline state across the melting point, which was determined by monitoring the time-dependence of the mean square displacement of the molecules, whereas, on cooling, the liquid state remained supercooled down to room temperature. The slope of the liquidus in the phase diagram between the low-pressure crystalline phase and the liquid phase was found to be positive, implying that the low-pressure crystalline phase has little connection with solid state amorphization. An expected overall pressure-temperature phase diagram of SnI 4 is discussed.

Section: Resultsmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Section: Methods Of MD Simulationsmentioning

confidence: 99%

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Search for precursor of pressure-induced amorphization of molecular crystal SnI4: Thermodynamic stability of low-pressure crystalline phase

The Journal of Chemical Physics

Sugiyama

Fujii

2000

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“…An order-of-magnitude difference of the molecular incompressibility seems to justify our previous modeling for molecular crystal SnI 4 , in which SnI 4 molecules were treated as rigid tetrahedrons [34,35]. When the model crystal was pressurized in the CP-I field, the molecules were found to rotate around 1 1 1 axes by about 1 • [34].…”

Section: Phase Transformationmentioning

confidence: 66%

Do SnI₄ molecules deform on heating and pressurization in the low-pressure crystalline phase?

Naruta

J. Phys.: Condens. Matter

Wakabayashi

et al. 2019

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A SnI 4 molecule lowers its symmetry from T d to C 3v on the liquid-liquid transition. Because it is possible to lower the molecular symmetry without violating the crystalline symmetry, it is worth examining whether the deformation occurs in the crystalline phase field. Extended x-ray absorption fine structure (EXAFS) measurements on the crystalline state were carried out to investigate the change in the environment around a Sn atom at high pressures and temperatures. We could not find clear evidence on the symmetry change of molecules even close to the melting points, where the melting curve becomes abnormally flat against pressure. Indeed, no inconsistency was found when we assumed that the coordination number of a Sn atom remains unchanged in the temperature and pressure range examined. The situation remains true when the system entered the high-pressure crystalline phase on compression. We can propose a consistent scenario as to the structural change on the phase transformation. The incompressibility of a SnI 4 molecule could be suitably quantified. The procedure enabled us to conclude the molecule is more than an order of magnitude incompressible than the lattice.

“…In the present model, which reproduces the properties of CP-I fairly well, 3) the SnI 4 molecules are regarded as rigid tetrahedra interacting with one another via the van der Waals force, the interaction center being the vertices of each tetrahedron between which we adopt the Lennard-Jones potential of the 12-6 type. The Nosé-Klein scheme 6) supplemented by the momentum scaling method 7) was employed to realize the isothermal-isobaric ensemble (see Ref.…”

mentioning

confidence: 99%

Molecular Dynamics Simulation Study on Melting and Liquid Properties of SnI₄

Prog. Theor. Phys. Suppl.

Sugiyama

Fujii

2000

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