Related papers: Properties of Vacancy Formation in He-4 hcp Crysta…
Diffusion and clustering of lattice vacancies in silicon as a function of temperature, concentration, and interaction range are investigated by Kinetic Lattice Monte Carlo simulations. It is found that higher temperatures lead to larger…
For nearly half a century the supersolid phase of matter has remained mysterious, not only eluding experimental observation, but also generating a great deal of controversy among theorists. Recent discovery of what is interpreted as a…
Ab initio molecular dynamic method within the framework of density functional theory is applied to analyze the structural and electronic properties of crystalline molecular hydrogen at temperature 100\,K. Pressure, pair correlation function…
Using the path-integral Monte Carlo method, we calculate the energy to form single and pair vacancies and interstitials in a two-dimensional Wigner crystal of electrons. We confirm that the lowest-lying energy defects of a 2D electron…
We study the hydrodynamics of quantum 4He crystal oscillations in a superfluid liquid with involving the dynamics of atomically rough surfaces. It is shown that, due to enhancement of the kinetic growth coefficient as the temperature…
The magnetic and iron vacancy orders in superconducting (Tl,Rb)2Fe4Se5 single-crystals are investigated by using a high-pressure neutron diffraction technique. Similar to the temperature effect, the block antiferromagnetic order gradually…
Defects are believed to play a fundamental role in the supersolid state of 4He. We have studied solid 4He in two dimensions (2D) as function of the number of vacancies n_v, up to 30, inserted in the initial configuration at rho = 0.0765…
In the study of phase transitions a very few models are accessible to exact solution. In the most cases analytical simplifications have to be done or some numerical technique has to be used to get insight about their critical properties.…
Results of X-ray diffraction experiments on solid oxygen at low temperature and at pressures up to 10 GPa are presented.A careful sample preparation and annealing around 240 K allowed to obtain very good diffraction patterns in the…
A new phase field crystal (PFC) type theory is presented, which accounts for the full spectrum of solid-liquid-vapor phase transitions within the framework of a single density order parameter. Its equilibrium properties show the most…
We model the low-temperature specific heat of solid $^4$He in the hexagonal closed packed structure by invoking two-level tunneling states in addition to the usual phonon contribution of a Debye crystal for temperatures far below the Debye…
We report the growth of mm-sized Pmnb-Li2FeSiO4 single crystals by means of the optical floating-zone method at high argon pressure and describe the conditions required for a stable growth process. The crystal structure is determined and…
Variational Monte Carlo method is used to calculate ground state properties of $^4$He droplets, containing 70, 112, 168, 240, 330, and 728 particles. The resulting particle and kinetic energy densities are used as an input in the…
In a cluster crystal, each lattice site is occupied by multiple soft-core particles. As the number density is increased at zero temperature, a `cascade' of isostructural phase transitions can occur between states whose site occupancy…
Several experimental studies have reported thermally activated behavior of the mechanical response of solid Helium-4 which does not fit into the model of thermally activated Frenkel pairs in an ideal crystal. The purpose of the present work…
A methodology for calculating the contribution of charged defects to the configurational free energy of an ionic crystal is introduced. The temperature-independent Wang-Landau Monte Carlo technique is applied to a simple model of a solid…
In the weakly non-ideal gas model [1], the Bose-Einstein condensation at constant pressure is considered. The temperature of transition to the state with condensate is found. Temperature dependences of the total density and condensate…
We have performed a Quantum Monte Carlo study of a two-dimensional bulk sample of interacting 1/2-spin structureless fermions, a model of $^3$He adsorbed on a variety of preplated graphite substrates. We have computed the equation of state…
We report ground state energies and structural properties for small helium clusters (4He) containing an H- impurity computed by means of variational and diffusion Monte Carlo methods. Except for 4He_2H- that has a noticeable contribution…
The diffusion Monte Carlo method is applied to describe a trapped atomic Bose-Einstein condensate at zero temperature, fully quantum mechanically and nonperturbatively. For low densities, $n(0)a^3 \le 2 \cdot 10^{-3}$ [n(0): peak density,…