title: Water nanodroplet thermodynamics: quasi-solid phase-boundary dispersivity.
abstract: It has long been puzzling that water nanodroplets undergo simultaneously "supercooling" at freezing and "superheating" at melting. Recent progress (Sun et al. J. Phys. Chem. Lett. 2013, 4, 2565, 3238) enables us to resolve this anomaly from the perspective of hydrogen bond (O:H-O) specific heat disparity. A superposition of the specific heat ηx(T) curves for the H-O bond (x = H) and the O:H nonbond (x = L) defines two intersecting temperatures that form the ice/quasi-solid/liquid phase boundaries. Molecular undercoordination (with fewer than four nearest neighbors in the bulk) stretches the ηH(T) curve by raising the Debye temperature ΘDH through H-O bond shortening and phonon stiffening. The ηH(T) stretching is coupled with the ηL(T) depressing because of the Coulomb repulsion between electron pairs on oxygen ions. The extent of dispersion varies with the size of a droplet that prefers a core-shell structure configuration-the bulk interior and the skin. Understandings may open an effective way of dealing with the thermodynamic behavior of water droplets and bubbles from the perspective of O:H-O bond cooperativity.
authors.affiliation: †Institute for Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China.|‡Institute of Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen 518060, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: †Institute for Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Sun
authors.affiliation: §Key Laboratory of Low-Dimensional Materials and Application Technology (MOE) and School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China.
authors.forename: Yongli
authors.initials: Y
authors.lastname: Huang
authors.affiliation: §Key Laboratory of Low-Dimensional Materials and Application Technology (MOE) and School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China.
authors.forename: Zengsheng
authors.initials: Z
authors.lastname: Ma
authors.affiliation: †Institute for Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China.
authors.forename: Xinjuan
authors.initials: X
authors.lastname: Liu
authors.affiliation: ∥State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Ji
authors.initials: J
authors.lastname: Zhou
authors.affiliation: ⊥School of Materials Science, Jilin University, Changchun 130012, China.
authors.forename: Weitao
authors.initials: W
authors.lastname: Zheng
authors.affiliation: #NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798.
authors.forename: Chang Q
authors.initials: CQ
authors.lastname: Sun