Optimized Geometry using the Conwell-Mizes

Optimized geometry using the Conwell-Mizes-jeyadev potential. 

The dramatic difference in the geometrical structure between the terminated and the periodic system is due to the abrupt cut-off in the external potential at the chain boundaries of the tenninated system. This is verified by performing a calculation for the two systems without any external 

THE EFFECT OF INTRA-CHAIN ELECTRON-ELECTRON INTERACTIONS. 

The dimerization order parameter and the net charge distribution of the optimized system with the full Hamiltonian is shown in Fig. 4, for the case of periodic boundary conditions (N=120, N3=10). In this case, the presentation is restricted to a periodic system since the results for a system with fixed-end boundary conditions are qualitatively the same (see discussion below). The bottom graph in Fig. 4 shows the total single particle potential which is the sum of the external potential and the potential energy due to the intra-chain Coulomb interaction. This potential is obtained by summing the terms in Eqs. (4), (5) and (7) at each site, n, along the chain. 

In contrast to the results obtained with the intra-chain Coulomb repulsion omitted, the abrupt cutoff in the external potential at the ends of the chain does no longer destroy the sohton lattice structure of the system with fixed end boundary conditions. This is due to a screening of the external potential by the large amount of electronic charge localized to the regions where the external potential has minima. Consequently, the depth of the potential minima becomes strongly reduced relative to the height of the potential wells between two solitons as well as relative to the potential at the chain ends. 

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