Dear Research Gate,
Is there any possibility for a system which is tetragonal at ambient condition and have a phase change tetragonal to cubic at high pressures, and as pressure still increases again the system going to initial phase (tetragonal).
Is it possible? If so any previous references are there?
Please help me.
The current behavior when pressure is applied is, logically, from a phase to another denser phase. Also the coordination number must increase, from low to a higher coordination, as the distances between atoms become shorter. Undegoing from a tetragonal phase, to a cubic phase and then to the previous tetragonal phase seems to me improbable.
With my best regards,
Pedro
as P. Grima Gallardo, this the (general) guideline. However, a size-driven[1] phase transition seem to break this guideline in nanomaterials[1,2]. So, if you accept a pressure driving force replacement by a stress[1] driving force then some nanomaterials' case studies[1,2] might be helpful.
1. Study of the tetragonal-to-cubic phase transition in PbTiO3 nanopowders http://iopscience.iop.org/article/10.1088/0953-8984/18/15/028/pdf
2. Smearing of Phase Transition due to a Surface Effect or a Bulk Inhomogeneity in Ferroelectric Nanostructures http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.94.107601
There are several factors which affect a phase transformation. It is perhaps theoretically possible to change pressure and temperature to come back into the same phase stability area. On the other hand, you don't exclude the formation of another tetragonal structure, only the crystal system. And it is not excluded that during a pressure-induced phase transformation the chemistry of the phase is slightly changing. Pedros rule is based on general experience and valid for the majority of phase transformations but I would not exclude such rare case per-se. In case of nano-materials several assumptions are no more correct so that from my point of view a "comparison" with common materials is possible but probably not very meaningful. Therefore, they are called by an extra term (nano-material). It is not the size which is important but the property change.
When the property is the balance from many competing factors then there appears an implicit[1]size[2] dependence of the (nano-size material) property.
1. Size dependence of the pressure-induced phase transition in nanocrystals https://arxiv.org/pdf/0801.0468.pdf, http://pubs.acs.org/doi/full/10.1021/jp077719e
2. Size dependence of the pressure-induced γ to α structural phase transition in iron oxide nanocrystals http://iopscience.iop.org/article/10.1088/0957-4484/16/12/013, http://iopscience.iop.org/article/10.1088/0957-4484/16/12/013#citations
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