𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Variational localized-site cluster expansions. VI. General theory revisited

✍ Scribed by D. J. Klein

Publisher
John Wiley and Sons
Year
1977
Tongue
English
Weight
888 KB
Volume
12
Category
Article
ISSN
0020-7608

No coin nor oath required. For personal study only.

✦ Synopsis

Abstract

A general and systematic localized‐site cluster expansion is described. It provides simple physically appealing and computationally feasible wave function ansätze, as well as, via extension of the cluster expansion, a unique expression for general, possibly exact, wave functions. We show that a variety of matrix element evaluation techniques are available and that they are sometimes exact though relatively simple. These techniques often proceed in terms of computational time proportional to the number of different types of sites, rather than their total number. Thus it seems we have a new and viable many‐body theory, which is expected to be most accurate and most readily implementable when a physical picture with slightly perturbed localized sites is relevant.

📜 SIMILAR VOLUMES

Variational localized-site cluster expan
Variational localized-site cluster expansions. VIII. Projection of spin symmetries
✍ D. J. Klein; M. A. García-Bach 📂 Article 📅 1977 🏛 John Wiley and Sons 🌐 English ⚖ 552 KB

## Abstract We investigate the total spin structure of an approximate localized‐site wave function for a collection of paramagnetic sites interacting so as to favor a singlet ground state. As the number of sites becomes infinite we obtain the distribution of weights of the different symmetry compon

Variational localized-site cluster expan
Variational localized-site cluster expansions. VII. Higher ansätze and the linear heisenberg model
✍ M. A. Garcíaa-bach; D. J. Klein 📂 Article 📅 1977 🏛 John Wiley and Sons 🌐 English ⚖ 703 KB

## Abstract The localized‐site cluster expansion technique is applied to the infinite linear Heisenberg model with both nearest‐neighbor and next nearest‐neighbor interactions. These cluster __ansätze__ are systematically studied and improved, up to the so‐called 5‐site approximation. Generally we