Structural studies of low temperature ice Ih using a central force potential model (original) (raw)
Related papers
Molecular multipole moments of water molecules in ice Ih
Chemical Physics, 1998
We have used an induction model including dipole, dipole-quadrupole, quadrupole-quadrupole polarizability and first hyperpolarizability as well as fixed octopole and hexadecapole moments to study the electric field in ice. The self-consistent induction calculations gave an average total dipole moment of 3.09 D, a 67% increase over the dipole moment of an isolated water molecule. A previous, more approximate induction model study by Coulson and Eisenberg [Proc. R. Soc. Lond. A 291, 445 (1966)] suggested a significantly smaller average value of 2.6 D. This value has been used extensively in recent years as a reference point in the development of various polarizable interaction potentials for water as well as for assessment of the convergence of water cluster properties to those of bulk. The reason for this difference is not due to approximations made in the computational scheme of Coulson and Eisenberg but rather due to the use of less accurate values for the molecular multipoles in these earlier calculations.
Chemical Physics, 1976
The equilibrium structure and vibrational frequencies of the water dimer and hexagonal ice have been calculated using the Harttee-Fock potential of Clementi andcoworkers and the correction fcr dispersion interactions of Koros and coworkers This correction term is proven to improve substantially the calculated results in the solid. The results obtained for the dimer were compared to other semiempiricaI and ab initio calcuIations and converging trends of the different studies are pointed out. Zero p&t energy effects were analyzed in hexagonal ice. These effects are shown to have little influence on determining the equilibrium structure of the crystal due to the peculiv behavior of the lattice frequencies as a function of the molar volume.
Multipole moments of water molecules in clusters and ice Ih from first principles calculations
The Journal of Chemical Physics, 1999
We have calculated molecular multipole moments for water molecules in clusters and in ice Ih by partitioning the charge density obtained from first principles calculations. Various schemes for dividing the electronic charge density among the water molecules were used. They include Bader's zero flux surfaces and Voronoi partitioning schemes. A comparison was also made with an induction model including dipole, dipole-quadrupole, quadrupole-quadrupole polarizability and first hyperpolarizability as well as fixed octopole and hexadecapole moments. We have found that the different density partitioning schemes lead to widely different values for the molecular multipoles, illustrating how poorly defined molecular multipoles are in clusters and condensed environments. For instance, the magnitude of the molecular dipole moment in ice Ih ranges between 2.3 D and 3.1 D depending on the partitioning scheme used. Within each scheme, though, the value for the molecular dipole moment in ice is larger than in the hexamer. The magnitude of the molecular dipole moment in the clusters shows a monotonic increase from the gas phase value to the one in ice Ih, with the molecular dipole moment in the water ring hexamer being smaller than the one in ice Ih for all the partitioning schemes used.
Single-crystal Ih ice surfaces unveil connection between macroscopic and molecular structure
Proceedings of the National Academy of Sciences of the United States of America, 2017
Physics and chemistry of ice surfaces are not only of fundamental interest but also have important impacts on biological and environmental processes. As ice surfaces-particularly the two prism faces-come under greater scrutiny, it is increasingly important to connect the macroscopic faces with the molecular-level structure. The microscopic structure of the ubiquitous ice Ih crystal is well-known. It consists of stacked layers of chair-form hexagonal rings referred to as molecular hexagons. Crystallographic unit cells can be assembled into a regular right hexagonal prism. The bases are labeled crystallographic hexagons. The two hexagons are rotated 30° with respect to each other. The linkage between the familiar macroscopic shape of hexagonal snowflakes and either hexagon is not obvious per se. This report presents experimental data directly connecting the macroscopic shape of ice crystals and the microscopic hexagons. Large ice single crystals were used to fabricate samples with the...
Structure order, local potentials, and physical anomalies of water ice
arXiv (Cornell University), 2014
This treatise deals with the structure order, local potentials, and physical anomalies demonstrated by water ice under compression, coordination number reduction, and thermal excitation. A "master-slave segmented H-bond (O:H-O)" forms a pair of asymmetric, H-bridged, coupled oscillators with short-range interactions and memory. This notation allows for specification of forces driving its cooperative relaxation. The cooperativity of the H-bond in length and energy and the associated binding electron entrapment and nonbonding electron polarization dictate the unusual performance of water ice. It has been revealed that: i) Compression shortens-and-stiffens the softer "O:H" bond and lengthens-and-softens the stiffer "H-O" covalent bond through repulsion between electron-pair on adjacent oxygen atoms, yielding the low compressibility, proton symmetrization, phase-transition temperature (T C) depression, softer phonon (< 300 cm-1) stiffening and stiffer phonon (> 3000 cm-1) softening; ii) Driven by the spontaneous H-O covalent bond contraction, molecular-undercoordination effects oppositely to compression. This process results in a supersolid phase that undergoes molecular size contraction and separation expansion, melting point (viscosity) elevation, binding energy entrapment, bonding charge densification, nonbonding lone electron polarization, stiffer phonon stiffening and softer phonon softening. The supersolidity of molecule clusters, surface skins, and ultrathin films of water makes them perform like ice and hydrophobic at the ambient temperature and frictionless of ice; iii) The disparity of the segmental specific heat discriminates the O:H from the H-O in responding to cooling, which shortens alternatively the segments in liquid, liquid-solid transition, solid, and ice at T < 80 K, resulting in four-region density and phonon-stiffness oscillation. The basic rule of sp 3-orbital hybridization of oxygen, detectable density, and the segmental length cooperativity have enabled a solution to discrepancies on the size, separation, structural order, and mass density of molecules packing in water and ice. It is emphasized that focusing on the statistical mean of all the cooperative parameters is more reliably revealing than on the instantaneous accuracy of one parameter at a time for the strongly correlated and fluctuating system of liquid water. Reconciling observations of O:H and H-O length symmetry under compression, O-O separation change at a surface and at cooling, solution clarifies: i) the preference of the fluctuated tetragonal structure of water, ii) the essence of inter electron-pair repulsion, and iii) the presence of the supersolid phase at regions consisting molecules with fewer than four neighbors. A combination of the Lagrangian vibration mechanics, molecular dynamics decomposition of volume evolution, and Raman spectroscopy of phonon relaxation has enabled probing of the asymmetric, local, short-range potentials pertaining to the O:H-O bond. Coulomb mediation of the intermolecular interaction results in the Hofmeister effect. Numerical solution to the Fourier equation for the fluid thermodynamics with the skin supersolidity resolved the Mpemba paradox that happens only in the non-adiabatic ambient. O:H-O bond has a memory to emit heat at a rate depending on the initial energy storage and the skin supersolidity creates the gradients of density, specific heat, and thermal conductivity. The memory of O:H-O bond may have implication to the signaling, messaging, and self-recovery of damage for living cells.
Structural Models of Water and Ice Regarding the Energy of Hydrogen Bonding
Nanotechnology Research and Practice, 2015
In this review it is reported about the research on the structure of water and ice and intermolecular water cyclic associates (clusters) with general formula (Н 2 О) n and their charged ionic clusters [(Н 2 О) n ] + and [(Н 2 О) n ]by means of computer modelling and spectroscopy methods as 1 Н-NMR, IR-spectroscopy, DNES, EXAFS-spectroscopy, X-Ray and neurons diffraction. The computer calculation of polyhedral nanoclusters (Н 2 О) n , where n = 3-20 are carried out. Based on this data the main structural mathematical models describing water structure (quasicrystalline, continious, fractal, fractal-clathrate) have been examined and some important physical characteristics were obtained. The average energy of hydrogen bonding (∆E H…O) between Н 2 О molecules in the process of cluster formation was measured by the DNES method compiles-0,1067±0,0011 eV. It was also shown that water clusters formed from D 2 О were more stable, than those ones from Н 2 О due to isotopic effects of deuterium.
Ab initio study of the structure and dynamical properties of crystalline ice
Phase Transitions, 2005
We investigated the structural and dynamical properties of a tetrahedrally coordinated crystalline ice from first principles based on density functional theory within the generalized gradient approximation with the projected augmented wave method. First, we report the structural behaviour of ice at finite temperatures based on the analysis of radial distribution functions obtained by molecular dynamics simulations. The results show how the ordering of the hydrogen bonding breaks down in the tetrahedral network of ice with entropy increase in agreement with the neutron diffraction data. We also calculated the phonon spectra of ice in a 3x1x1 supercell by using the direct method. So far, due to the direct method used in this calculation, the phonon spectra is obtained without taking into account the effect of polarization arising from dipole-dipole interactions of water molecules which is expected to yield the splitting of longitudinal and transverse optic modes at the Gamma-point. The calculated longitudinal acoustic velocities from the initial slopes of the acoustic mode is in a reasonable agreement with the neutron scatering data. The analysis of the vibrational density of states shows the existence of a boson peak at low energy of translational region a characteristic common to amorphous systems.
Car-Parrinello Molecular Dynamics Study for the Isotope Effect on OH Vibration in Ice Ih
Bulletin of the Korean Chemical Society
The stretching vibration of OH of ice Ih is studied by Car-Parrinello molecular dynamics in regarding the effect of mixed H/D contamination while the vibrational spectrum is considered by velocity-velocity autocorrelations of the sampled ensemble. When hydrogen atoms are immersed randomly into the deuterated ice, a typical vibrational frequency of OH stretching mode is observed to be similar to that from the pure H 2 O ice. When focusing on the correlation of isolated neighboring OH stretching, a narrower and blue shifted peak is observed at the high frequency range as a result of the screening from the complex many body correlations by D 2 O environment. It is also specifically related to the symmetric intermolecular correlations between neighboring OH stretching modes. More enhanced high frequency range can be explained by the expansion of such two body correlations to collective many body correlations among all possible OH stretching modes. This contribution becomes important when it involves in chemical interactions via excitation of such vibrational states.
De glaciēbus or deductive molecular mechanics of ice polymorphs
Theoretical Chemistry Accounts, 2018
Yet in 1960s Del Re with coworkers considered the electronic structure of organic molecules using hybrid orbitals. They studied the simplest molecules: CH 4 , NH 3 , H 2 O, and more complex ones: cyclopropane, cyclobutane, cubane, using either the optimal overlap or maximal localization principles to determine the hybrids. Later Malrieu with coworkers used hybrid orbitals in the PCILO method. Later, we determined either the form and orientation of the hybrid orbitals or two-electron functions of the two-center bonds constructed on the basis of these hybrids from the minimum condition for total electronic energy as implemented in the SLG method. This gave us significant improvement in the efficiency: the dependence of the required computational resources on the molecule size reduces down to O(N). The paradigm based on the usage of the variation principle for determination of either the hybrid orbitals or the elements of the reduced density matrices in their basis allows one to formulate and prove exact statements about electronic structure. We start from establishing the energy expression for highly symmetric non-molecular ice X and prove mathematically the stability of this polymorph above a critical pressure. Below it, we derive the pressure dependence of the interaction energy of the effective dipoles emerging in the system when the symmetric layout of the hydrogen atoms, specific for ice X, breaks down. This reproduces semiquantitatively the characteristic and unusual (as compared to the others-practically vertical) form of the boundary between the areas of the ordered and disordered ice VIII and VII. We also discuss the possibility of describing the differences between the ice phases existing at lower pressures (down to normal) by including the long-range electrostatic contributions: charge-charge and dipole-dipole in the crystal energy.
A powerful computational crystallography method to study ice polymorphism
The Journal of Chemical Physics, 2011
Classical Molecular Dynamics (MD) simulations are employed as a tool to investigate structural properties of ice crystals under several temperature and pressure conditions. All ice crystal phases are analyzed by means of a computational protocol based on a clustering approach following standard MD simulations. The MD simulations are performed by using a recently published classical interaction potential for oxygen and hydrogen in bulk water, derived from neutron scattering data, able to successfully describe complex phenomena such as proton hopping and bond formation/breaking. The present study demonstrates the ability of the interaction potential model to well describe most ice structures found in the phase diagram of water and to estimate the relative stability of sixteen known phases through a cluster analysis of simulated powder diagrams of polymorphs obtained from MD simulations. The proposed computational protocol is suited for automated crystal structure identification.