Density functional molecular dynamical simulations have been performed on Ga17 and Ga13 clusters to understand the recently observed higher-than-bulk melting temperatures in small gallium clusters [Phys. Rev. Lett. 91, 215508 (2003)]]. The specific-heat curve, calculated with the multiple-histogram technique, shows the melting temperature to be well above the bulk melting point of 303 K, viz., ...

We re-examine the calculation of the bulk modulus of random networks with a variable mean coordination 〈r〉 that ranges from 〈r〉 = 4 down through the phase transition from rigid to floppy that occurs at around 〈r〉 = 2.4. In contrast to previous workers, we use random-network models, rather than depleted diamond lattices, so our results are more relevant to glasses. We find that the bulk modulus ...

A microscopic empirical model of bulk modulus based on atomic-scale parameters is proposed. These parameters include the bond length, the effective bonded valence electron (EBVE) number, and the coordination number product of two bonded atoms, etc. The estimated bulk moduli from our model are in good agreement with experimental values for various polar covalent crystals including ionic crystals...

Constitutional dynamic chemistry (CDC) features the use of reversible linkages at both molecular and supramolecular levels, including reversible covalent bonds (dynamic covalent chemistry, DCC) and noncovalent interactions (dynamic noncovalent chemistry, DNCC). Due to its inherent reversibility and stimuli-responsiveness, CDC has been widely utilized as a powerful tool for the screening of bioa...

The dream to prepare well-defined materials drives the methodological evolution for molecular synthesis, structural control and manufacturing. Among various methods, chemical approaches design, synthesize, engineer small molecules, polymers networks offer fundamental strategies. Merging covalent bonds non-covalent interactions into one method establish a complex composition specific functions, ...

The polymerization of 1,4-diethynylbenzene was studied on a Cu(111) surface using scanning tunneling microscopy (STM) under ultra-high vacuum conditions. Thermal activation yielded disordered covalent networks, where distinct basic structural motifs indicate different coupling reactions.

Covalent organic framework (COF) particles with hydroxy groups and well-defined micropores have been synthesized used as novel carriers to load a metallocene catalyst—Cp2ZrCl2. The resulting supported catalyst, which had high specific surface area, demonstrated higher catalytic activity, better thermal tolerance, unique nanoconfinment effect during ethylene polymerization, producing polyethylen...

Abstract Group transfer polymerization (GTP) is a method developed to obtain targeted (meth)acrylic polymers in solution at ambient temperatures. In this work, it employed with methacrylic monomers low Ð bulk. regard, different initiator systems that exhibit mechanisms are compared concerning the molecular weight, polydispersity and double bond conversion of resulting bulk polymers. The respect...