Molecular Clusters, Skins, and Ultrathin Films

Molecular under-coordination effects oppositely to compression. 

Spontaneous H-0 contraction elongates and polarizes the 0 H bond significantly via inter electron-pair repulsion. 

Under-coordinated H2O molecules shrink in size but enlarge their separation. The shortening of the H-0 bond entraps bonding electrons and raises the local density, which in turn polarizes the lone pairs of electrons on oxygen. 

The stiffening of the shortened H-O bond increases the magnitude of the O Is shift, causes the blue shift of the H-0 phonon frequencies, and elevates the T of molecular clusters and ultrathin films of water, which gives rise to their supersolid phase of elastic, hydrophobic, ice-like, polarized with ultra-low-density. 

Relaxation of the Chemical Bond, Springer Series in Chemical Physics 108, DOI 10.1007/978-981-4585-21-7 35, Springer Science+Business Media Singapore 2014 

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The stiffening of the H-0 bond increases the O Is core-level shift, causes the blueshift of the H-0 phonon frequency, and elevates the melting point of water molecular clusters, surface skins, and ultrathin films of water. 

The encapsuled and the free-standing (H20)n molecular clusters, surface skins, or ultrathin films of water should share the same entity of bond order deficiency to follow the BOLS premise without exception. However, the involvement of the weak lone pair interaction and the interelectron-pair repulsion prevents the two segments of the H-bond from following the BOLS mechanism simultaneously. The binding energy difference between the 0 H and H-O and the presence of the interelectron-pair repulsion define the H-O covalent bond to be the master that contracts by a smaller degree than which the BOLS notation predicts. The contraction of the H-O bond lengthens and softens the slave 0 H bond by repulsion. 

H-O bond contraction. Coulomb repulsion, and dual-process polarization drive the supersolidity with multiple features. The molecular separation doo = d + dn grows and molecular size d shrinks simultaneously at the skins because of the molecular under-coordination [21]. The H-0 bond contraction follows the rule of BOLS correlation the doo expansion results from the Coulomb repulsion between electron pairs on adjacent oxygen atoms [21, 24]. The polarization of water molecules in the molecular clusters [25, 26], surface skins, or ultrathin films of water is related to the molecule volume expansion because of the molecular charge conservation. The undercoordination-induced polarization lowers the work function of the bound electrons [6]. 

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