arXiv subjects

Klaus Doll

Publications and source records attributed to Klaus Doll.

8 recordsLinked to original sources

arXiv1998

Closed-shell interaction in silver and gold chlorides

Hartree-Fock and coupled-cluster calculations have been performed for cubic AgCl and for AuCl having a cubic or the observed structure with space group I4_1/amd. Cohesive energies and lattice constants are in excellent agreement with experiment for AgCl; for AuCl we find good agreement, and the experimental structure is correctly predicted to be lower in energy than the cubic one. Electron-correlation effects on lattice constants are very large, of up to 0.8 Åfor cubic AuCl. We especially discuss the strength of the closed-shell interactions, and for the first time a quantitative analysis of the so-called "aurophilic" Au(I)-Au(I) interaction is presented in solids.

cond-mat.mtrl-sci↗

arXiv1998

Ground-state properties of rutile: electron-correlation effects

Electron-correlation effects on cohesive energy, lattice constant and bulk compressibility of rutile are calculated using an ab-initio scheme. A competition between the two groups of partially covalent Ti-O bonds is the reason that the correlation energy does not change linearly with deviations from the equilibrium geometry, but is dominated by quadratic terms instead. As a consequence, the Hartree-Fock lattice constants are close to the experimental ones, while the compressibility is strongly renormalized by electronic correlations.

cond-mat.mtrl-sci↗

arXiv1998

Ground state properties of heavy alkali halides

We extend previous work on alkali halides by calculations for the heavy-atom species RbF, RbCl, LiBr, NaBr, KBr, RbBr, LiI, NaI, KI, and RbI. Relativistic effects are included by means of energy-consistent pseudopotentials, correlations are treated at the coupled-cluster level. A striking deficiency of the Hartree-Fock approach are lattice constants deviating by up to 7.5 % from experimental values which is reduced to a maximum error of 2.4 % by taking into account electron correlation. Besides, we provide ab-initio data for in-crystal polarizabilities and van der Waals coefficients.

cond-mat.mtrl-sci↗

arXiv1997

Cohesive properties of alkali halides

We calculate cohesive properties of LiF, NaF, KF, LiCl, NaCl, and KCl with ab-initio quantum chemical methods. The coupled-cluster approach is used to correct the Hartree-Fock crystal results for correlations and to systematically improve cohesive energies, lattice constants and bulk moduli. After inclusion of correlations, we recover 95-98 % of the total cohesive energies. The lattice constants deviate from experiment by at most 1.1 %, bulk moduli by at most 8 %. We also find good agreement for spectroscopic properties of the corresponding diatomic molecules.

cond-mat.mtrl-sci↗

arXiv1997

A Quantum Chemical Approach to Cohesive Properties of NiO

We apply ab-initio quantum chemical methods to calculate correlation effects on cohesive properties of NiO, thereby extending a recently proposed scheme to transition metal oxides with partially filled $d$-bands. We obtain good agreement with experiment for the cohesive energy and show that the deviation of the lattice constant at the Hartree-Fock level is mainly due to van der Waals-like interactions. Correlations enhance the stability of the magnetic ground state found at the Hartree-Fock level.

cond-mat.mtrl-sci↗

arXiv1996

Correlation effects in MgO and CaO: Cohesive energies and lattice constants

A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using ab-initio quantum chemical methods for evaluating individual increments, we obtain 80% of the difference between the experimental and Hartree-Fock cohesive energies. Lattice constants corrected for correlation effects deviate by less than 1% from experimental values, in the case of MgO and CaO.

mtrl-th↗

arXiv1996

Metal to Insulator Transition in the 2-D Hubbard Model: A Slave Boson Approach

We use the Kotliar-Ruckenstein slave boson technique to treat the strong correlation of the Hubbard model. In a first part we discuss the metal to insulator transition that is occurring on the honeycomb lattice at half filling. We find the critical value for the interaction strength to be U/t=3.1. Above it a gap opens in the spectrum which behaves like (U-U_c) in the vicinity of the transition, and like U for strong coupling. In a second part we calculate the phase diagram of the Hubbard model on the square lattice at finite temperature. The Mermin-Wagner theorem is fulfilled in the largest part of the phase diagram. In the strong coupling regime, the uniform magnetic susceptibility shows a maximum in its doping dependence in agreement with numerical simulations.

cond-mat↗

arXiv1995

Correlation effects in ionic crystals: I. The cohesive energy of MgO

High-level quantum-chemical calculations, using the coupled-cluster approach and extended one-particle basis sets, have been performed for (Mg2+)n (O2-)m clusters embedded in a Madelung potential. The results of these calculations are used for setting up an incremental expansion for the correlation energy of bulk MgO. This way, 96% of the experimental cohesive energy of the MgO crystal is recovered. It is shown that only 60% of the correlation contribution to the cohesive energy is of intra-ionic origin, the remaining part being caused by van der Waals-like inter-ionic excitations.

cond-mat↗