Local structural features of metallic alloys: Ni<inf>33</inf>Zr<inf>67</inf> and Ni<inf>50</inf>Zr<inf>50</inf>

In this work we present the results of computer simulations molecular dynamics of the metallic alloys: Ni33Zr67 and Ni50Zr50. The critical glass-forming temperatures are defined from the behavior change of theWendt-Abraham parameters of the studied systems. We have found that the increase in the concentration of nickel in the system NiZr leads to displacement of the critical glass-forming temperature in higher temperature region. It is shown that the structural transformations which were observed in the Ni50Zr50 system are not related with crystallization processes

Dynamics of a network of hydrogen bonds upon water electrocrystallization

Computer simulation is employed to study the dynamics of a network of hydrogen bonds and the structural properties of water placed between graphene layers. The presence of the graphene walls has been shown to substantially affect the water phase diagram. Glass transition processes are observed in the system, and liquid water completely passes to an amorphous state. Moreover, it has been established that the imposition of an external electric field with strength E ≥ 0.5 V/Å on the system subjected to increased pressure results in structural ordering of water. It has been found that water located between graphene layers is transformed into Ic cubic ice. The electrocrystallization of water has been shown to substantially change the dynamics of the network of hydrogen bonds. © 2013 Pleiades Publishing, Ltd

Structural and dynamic features of water and amorphous ice

© 2017, Pleiades Publishing, Ltd.Structural properties and microscopic dynamics of water and amorphous ice have been studied by the molecular dynamics method. It has been found that the distribution function of the tetrahedricity parameter exhibits two ranges, which correspond to local molecular formations with low and high degrees of tetrahedricity. The number of molecular clusters with a high degree of tetrahedricity grows as temperature decreases. It has been shown that the vibrational density of states comprises two vibrational modes. A low-frequency vibrational mode strongly depends on pressure and is almost independent of temperature, while a high-frequency mode is relevant to the pressure-independent heat motion of molecules. The geometric criterion of hydrogen bonds has been used to evaluate their continuous lifetime as depending on temperature for molecules with different coordination values. The average lifetime of a hydrogen bond substantially depends on the coordination of molecules, with the temperature dependence of the coordination obeying the activation dynamics

Microscopic collective dynamics of water

© 2016, Pleiades Publishing, Ltd.Data obtained on microscopic collective excitations in water by molecular dynamics simulation within the framework of the coarse-grained mW-model of the intermolecular interaction potential for water are reported. The calculated spectra of the dynamic structure factor and spectral densities of time correlation functions of longitudinal and transverse currents reveal the existence of propagating collective excitations of longitudinal and transverse polarization in water for a wide range of wavenumbers. The dynamics of fluctuations in the particle number density is analyzed within the framework of a microscopic theory that takes into account only the structural features of a system. The theoretically calculated data on the spectra of dynamic structure factor in a wavenumber range of 0.13–0.48 Å–1 are in good agreement with the results of molecular dynamics simulation

Atomic collective excitations in liquid lead

© 2014, Pleiades Publishing, Inc. The atomic dynamics of liquid lead at the temperature T = 600 K has been simulated on the basis of the embedded atom model potential (the “embedded” atom model making it possible to effectively take into account the many-particle interactions) in order to study the mechanisms of formation of the atomic collective excitations. Spectra of the dynamic structure factor S(k, ω) and the spectral densities of the time correlation functions of the longitudinal (formula presented.) (k, ω) and transverse (formula presented.) (k, ω) currents have been calculated for the wavenumber region 0.11 Å−1 ≤ k ≤ 2.01 Å−1. It has been established that the dynamics of density fluctuations is characterized by two dispersion “acoustic-like” branches of the longitudinal and transverse polarization