TY - JOUR
T1 - Nonclassical Crystal Growth as Explanation for the Riddle of Polarity in Centrosymmetric Glycine Crystals
AU - Meirzadeh, Elena
AU - Sapir, Liel
AU - Cohen, Hagai
AU - Cohen, Sidney R.
AU - Ehre, David
AU - Harries, Daniel
AU - Lahav, Meir
AU - Lubomirsky, Igor
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/11/9
Y1 - 2016/11/9
N2 - The riddle of anomalous polar behavior of the centrosymmetric crystal of α-glycine is resolved by the discovery of a polar, several hundred nanometer thick hydrated layer, created at the {010} faces during crystal growth. This layer was detected by two independent pyroelectric analytical methods: (i) periodic temperature change technique (Chynoweth) at ambient conditions and (ii) contactless X-ray photoelectron spectroscopy under ultrahigh vacuum. The total polarization of the surface layer is extremely large, yielding ≈1 μC·cm-2, and is preserved in ultrahigh vacuum, but disappears upon heating to 100 °C. Molecular dynamics simulations corroborate the formation of polar hydrated layers at the sub-microsecond time scale, however with a thickness of only several nanometers, not several hundred. This inconsistency might be reconciled by invoking a three-step nonclassical crystal growth mechanism comprising (i) docking of clusters from the supersaturated solution onto the evolving crystal, (ii) surface recognition and polar induction, and (iii) annealing and dehydration, followed by site-selective recrystallization.
AB - The riddle of anomalous polar behavior of the centrosymmetric crystal of α-glycine is resolved by the discovery of a polar, several hundred nanometer thick hydrated layer, created at the {010} faces during crystal growth. This layer was detected by two independent pyroelectric analytical methods: (i) periodic temperature change technique (Chynoweth) at ambient conditions and (ii) contactless X-ray photoelectron spectroscopy under ultrahigh vacuum. The total polarization of the surface layer is extremely large, yielding ≈1 μC·cm-2, and is preserved in ultrahigh vacuum, but disappears upon heating to 100 °C. Molecular dynamics simulations corroborate the formation of polar hydrated layers at the sub-microsecond time scale, however with a thickness of only several nanometers, not several hundred. This inconsistency might be reconciled by invoking a three-step nonclassical crystal growth mechanism comprising (i) docking of clusters from the supersaturated solution onto the evolving crystal, (ii) surface recognition and polar induction, and (iii) annealing and dehydration, followed by site-selective recrystallization.
UR - http://www.scopus.com/inward/record.url?scp=84994514899&partnerID=8YFLogxK
U2 - 10.1021/jacs.6b09190
DO - 10.1021/jacs.6b09190
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C2 - 27779856
AN - SCOPUS:84994514899
SN - 0002-7863
VL - 138
SP - 14756
EP - 14763
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 44
ER -