Pressure-induced isosymmetric phase transition in biurea

Craig L. Bull; Nicholas P. Funnell; Christopher J. Ridley; Colin R. Pulham; Paul L. Coster; James P. Tellam; William G. Marshall

doi:10.1039/c9ce01028a

Pressure-induced isosymmetric phase transition in biurea

Craig L. Bull, Nicholas P. Funnell, Christopher J. Ridley, Colin R. Pulham, Paul L. Coster, James P. Tellam, William G. Marshall

Research output: Contribution to journal › Article › peer-review

6 Scopus citations

Abstract

We report a pressure-induced transition to a new crystalline phase of biurea (C₂D₆N₄O₂). Neutron-powder diffraction and Raman spectra, measured up to 3.89 GPa reveal this transition to be isosymmetric, where substantial intramolecular reorientation leads to an abrupt decrease in unit cell volume at ∼0.6 GPa and an increase in some intermolecular contact distances. DFT and vibrational energy calculations suggest that the ambient pressure phase is stabilised by zero point energy and entropy, until the pressure-volume-driven transition at 0.6 GPa.

Original language	English
Pages (from-to)	5872-5881
Number of pages	10
Journal	CrystEngComm
Volume	21
Issue number	39
DOIs	https://doi.org/10.1039/c9ce01028a
State	Published - 2019
Externally published	Yes

Funding

This work has been supported by facilities made available by STFC. We acknowledge ISIS Neutron and Muon Facility for access to the PEARL and TOSCA instruments.59 We thank Dr. Svemir Rudic, Dr. Jeff Armstrong, and Dr. Hamish Cavaye for assistance with the INS measurements and useful discussion. Finally, we acknowledge the computing resources provided the STFC Scientific Computing Department's SCARF cluster.

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title = "Pressure-induced isosymmetric phase transition in biurea",

abstract = "We report a pressure-induced transition to a new crystalline phase of biurea (C2D6N4O2). Neutron-powder diffraction and Raman spectra, measured up to 3.89 GPa reveal this transition to be isosymmetric, where substantial intramolecular reorientation leads to an abrupt decrease in unit cell volume at ∼0.6 GPa and an increase in some intermolecular contact distances. DFT and vibrational energy calculations suggest that the ambient pressure phase is stabilised by zero point energy and entropy, until the pressure-volume-driven transition at 0.6 GPa.",

author = "Bull, {Craig L.} and Funnell, {Nicholas P.} and Ridley, {Christopher J.} and Pulham, {Colin R.} and Coster, {Paul L.} and Tellam, {James P.} and Marshall, {William G.}",

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T1 - Pressure-induced isosymmetric phase transition in biurea

AU - Bull, Craig L.

AU - Funnell, Nicholas P.

AU - Ridley, Christopher J.

AU - Pulham, Colin R.

AU - Coster, Paul L.

AU - Tellam, James P.

AU - Marshall, William G.

PY - 2019

Y1 - 2019

N2 - We report a pressure-induced transition to a new crystalline phase of biurea (C2D6N4O2). Neutron-powder diffraction and Raman spectra, measured up to 3.89 GPa reveal this transition to be isosymmetric, where substantial intramolecular reorientation leads to an abrupt decrease in unit cell volume at ∼0.6 GPa and an increase in some intermolecular contact distances. DFT and vibrational energy calculations suggest that the ambient pressure phase is stabilised by zero point energy and entropy, until the pressure-volume-driven transition at 0.6 GPa.

AB - We report a pressure-induced transition to a new crystalline phase of biurea (C2D6N4O2). Neutron-powder diffraction and Raman spectra, measured up to 3.89 GPa reveal this transition to be isosymmetric, where substantial intramolecular reorientation leads to an abrupt decrease in unit cell volume at ∼0.6 GPa and an increase in some intermolecular contact distances. DFT and vibrational energy calculations suggest that the ambient pressure phase is stabilised by zero point energy and entropy, until the pressure-volume-driven transition at 0.6 GPa.

UR - http://www.scopus.com/inward/record.url?scp=85073195396&partnerID=8YFLogxK

U2 - 10.1039/c9ce01028a

DO - 10.1039/c9ce01028a

M3 - Article

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VL - 21

SP - 5872

EP - 5881

JO - CrystEngComm

JF - CrystEngComm

IS - 39

ER -

Pressure-induced isosymmetric phase transition in biurea

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