Theory of Electronic Structures and Lattice Distortions in Polyacetylene and Itinerant Peierls Systems. I UHF Transfer Matrix Method Adapted to the Long Range Coulomb Interaction and UHF States in Regular Bond Alternated Lattice
Theory of Electronic Structures and Lattice Distortions in Polyacetylene and Itinerant Peierls Systems. I UHF Transfer Matrix Method Adapted to the Long Range Coulomb Interaction and UHF States in Regular Bond Alternated Lattice
复制标题
聚乙炔和巡回 Peierls 系统中的电子结构和晶格畸变理论。
DOI：
10.1143/ptp.67.41
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发表时间：
1982
影响因子：
--
通讯作者：
M. Sasai
中科院分区：
文献类型：
--
作者：
H. Fukutome;M. Sasai
我们在这一系列的巡回Peierls系统的理论，主要目的是研究聚乙炔。为了研究长程库仑相互作用在Peierls系统中的电子结构和晶格畸变中的作用，我们发展了一种适用于该系统的转移矩阵方法。无限制Hartree·Fock（UHF）近似。该方法使得计算任意非周期晶格中的UHF态和平衡晶格几何成为可能。应用这种方法，我们得到了规则晶格下可能成为HF基态的UHF态。至少有八个这样的UHF状态，它们通过自旋和电荷密度的长程有序和键序来区分。最近邻交换相互作用是产生如此丰富的UHF态的原因。利用能很好地再现小分子共轭烃的光谱和平衡几何的哈密顿量和弹性势的参数化，计算了反式聚乙炔的键交替势和带隙.键交替势对最近邻库仑相互作用的强度非常敏感。具有快速阻尼的库仑势阻止了键的交替。只要聚乙炔中的库仑相互作用类似于小的共轭烃中的库仑相互作用，则带隙远大于最低吸收带的能量2eV，这表明吸收带的激子性质。我们还对具有反铁磁自旋序和晶格二聚化的巡游自旋Peierls系统作了说明性计算。
We develop in this series a theory of itinerant Peierls systems that mainly aims to study polyacetylene. In order to investigate roles of the long range Coulomb interaction in electronic structures and lattice distortions in a Peierls system, we develop a transfer matrix technique adapted to the. unrestricted Hartree·Fock (UHF) approximation. The method makes it pos sible to calculate UHF states and equilibrium lattice geometries in a lattice with any aperiodic structure due to the presence of solitons. Applying the method, we obtain the UHF states in the case of regular lattice that may become the HF ground state. There are at least eight such UHF states which are distinguished by the long range orders in the spin and charge densities and the bond orders. The nearest neighbour exchange interaction is responsible to produce such plentiful UHF states. We calculate the bond alternation potential and the band gap in trans polyacetylene using paramet rizations of the Hamiltonian and the elastic potential that are able to well reproduce spectra and equilibrium geometries of small conjugated hydrocarbons. The bond alternation potential is very sensitive to the strength of the nearest neighbour Coulomb interaction. The Coulomb potential with fast damping prevents the bond alternation. The band gap is much larger than the energy 2 eV of the lowest absorption band as long as the Coulomb interaction in poly acetylene is similar to that in small conjugated hydrocarbons, suggesting the excitonic nature of the absorption band. We make also an illustrative calculation for an itinerant spin Peierls system with an antiferromagnetic spin order as well as a lattice dimerization.