scholarly journals Erratum: “Universality of the onset of activated transport in Lennard-Jones liquids with tunable coordination: Implications for the effects of pressure and directional bonding on the crossover to activated transport, configurational entropy, and fragility of glassforming liquids” [J. Chem. Phys. 136, 084504 (2012)]

2012 ◽  
Vol 136 (24) ◽  
pp. 249901
Author(s):  
Pyotr Rabochiy ◽  
Vassiliy Lubchenko
Keyword(s):  
Configurational Entropy ◽  
Chem Phys ◽  
Lennard Jones ◽  
Directional Bonding

Publisher's Note: “Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems” [J. Chem. Phys. 134, 164505 (2011)]

2011 ◽  
Vol 135 (13) ◽  
pp. 139901
Author(s):  
Thomas B. Schrøder ◽  
Nicoletta Gnan ◽  
Ulf R. Pedersen ◽  
Nicholas P. Bailey ◽  
Jeppe C. Dyre
Keyword(s):  
Chem Phys ◽  
Lennard Jones

Incommensurately modulated structure of morpholinium tetrafluoroborate and configurationalversuschemical entropies at the incommensurate and lock-in phase transitions

2017 ◽  
Vol 73 (5) ◽  
pp. 836-843
Author(s):  
Leila Noohinejad ◽  
Sander van Smaalen ◽  
Václav Petříček ◽  
Andreas Schönleber
Keyword(s):  
Phase Transitions ◽  
Conformational Changes ◽  
Ferroelectric Properties ◽  
Configurational Entropy ◽  
Chem Phys ◽  
Ambient Conditions ◽  
Disorder Phase Transition ◽  
The Difference ◽  
A Minor ◽  
Transition Entropy

Morpholinium tetrafluoroborate, [C4H10NO]+[BF4]−, belongs to a class of ferroelectric compoundsABX4. However, [C4H10NO]+[BF4]−does not develop ferroelectric properties because the incommensurate phase belowTc,I= 153 K is centrosymmetric with superspace groupPnam(σ100)00sand σ1= 0.42193 (12) atT= 130 K; the threefold superstructure belowTc,II= 117–118 K possesses the acentric but non-ferroelectric space groupP212121. At ambient conditions, [C4H10NO]+[BF4]−comprises orientationally disordered [BF4]−anions accommodated in cavities between four morpholinium cations. A structure model for the incommensurately modulated phase, which involves modulated orientational ordering of [BF4]−together with modulated distortions and displacements of the morpholinium ions is reported. A mechanism is proposed for the phase transitions, whereby at low temperatures morpholinium cations are shaped around the tetrafluoroborate anion in order to optimize the interactions with one orientation of this anion and, thus, forcing [BF4]−into this orientation. This mechanism is essentially different from a pure order–disorder phase transition. It is supported by consideration of the transition entropy. The difference in configurational entropy between the disordered and incommensurate phases has been computed from the structure models. It is shown to be much smaller than the experimental transition entropy reported by Owczareket al.[Chem. Phys.(2011),381, 11–20]. These features show that the order–disorder contribution is only a minor contribution to the transition entropy and that other factors, such as conformational changes, play a larger role in the phase transitions.

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