Hartree-Fock Cluster Investigation of 135Ba in YBa2Cu3O7 and YBa2Cu4O8 Systems

Sudha Srinivasa, S. B. Sulaimanb, N. Sahooc,d and T. P. Dasd,*

a  Department of Physics, Central Michigan University, Mount Pleasant, MI, 48859, USA
b  Department of Physics and Information Technology Centre, Universiti Sains Malaysia, Minden 11800, Penang, Malaysia
c  Department of Radiation Oncology, The Albany Medical College, Albany, NY, 12208, USA
d  Department of Physics, State University of New York at Albany, Albany, NY, 12222, USA

*  Corresponding Author: FAX 1-(518)-442-5260

We have studied the 135Ba nuclear quadrupole interaction in YBa2Cu3O7 and YBa2Cu4O8 using the first-principles Hartree-Fock Cluster procedure [1]. This completes the investigations by our group for 135Ba in the series involving 1236, 1237, 1248 systems all by the same procedure, the system YBa2Cu3O6 having been studied earlier [2]. The available orthorhombic crystal structures for the 1237 [3] and 1248 [4] with one and two formula units in each cell respectively were utilized. The clusters (BaO4)-2 and the slightly larger one (BaO6)-4 were used. The former was used because it was expected that Ba+2 would be fairly ionic with its closed shell configuration and using the four nearest oxygen neighbors of Ba+2 would be adequate. However to test the correctness of this assumption the larger cluster was also used, involving in addition to the nearest neighbors of Ba+2, some of the next nearest oxygen neighbors. But no appreciable change in the e2qQ and h for 135Ba were found. Large basis sets involving (4333/4333/43) [5] optimized for the Ba+2 ion and a (4322211/42211/44) basis set [5] were used for Ba+2 ion while for O-, the basis set (73111/5111) [6] was used. The convergence with respect to basis set for the 135Ba e2qQ and h were studied and found to be satisfactory by using the two basis sets for Ba+2 and uncontracting the O-1 basis set.

Our results for the 135Ba e2qQ and h for YBa2Cu3O7 and YBa2Cu4O8 together with the experimental results are listed in Table 1. The results of the earlier Hartree-Fock Cluster investigation and experimental results are also listed for ready reference and comparison with the other two systems. The value of Q (135Ba) used to obtain the coupling constants e2qQ for the 1237 and 1248 systems was 0.160 (3) barns [7].
 

Table 1. Results of our Present and Earlier Investigations of 135Ba in Copper Oxide High Tc Systems and Experimental Data.
System
 
Theoretical
   
Experimental
 
 
e2qQ (MHz)
h
Principal axis (Z)
e2qQ (MHz)
h
Principal axis (Z)
YBa2Cu4O8
44.0a
0.72a
a axisa
37.1c
Not available
Not available
YBa2Cu3O7
38.7a
0.82a
a axisa
32.0d
0.9d
c axisd
       
29.0e
0.8e
a axise
YBa2Cu4O8
46.0b
0.0b
c axisb
54.0f
0.0f
c axisf

a Present work b Ref. 2. c Ref. 8. d Ref. 9. e Ref. 10. f Ref. 11.
 

Thus, there is overall good agreement between the experimental and theoretical results for e2qQ, h and Principal Z-axis. However, in the case of YBa2Cu3O7 there is a difference in the experimentally observed direction of the Z axis between Ref. 9 and 10.
Likely physical reasons for the trend in the nuclear quadrupole interaction properties between the three compounds will be discussed. Comparison will be made  between our results and earlier band structure results [10] with the Linearized Augment Plane Wave procedure using the Localized Density Functional Approximation.

[1]   “Electronic Properties of Solids Using Cluster Methods”, Ed. T. A. Kaplan and S. D. Mahanti, Plenum Press, New York (1995).
[2]   S. B. Sulaiman, N. Sahoo, T. P. Das and O. Donzelli, Phys. Rev. B45, 7383 (1992).
[3]   M. A. Beno et al., Appl. Phys. Lett. 51, 57 (1987).
[4]   P. Fischer et al., Solid State Comm. 69, 531 (1989).
[6]   S. Huzinaga, “Gaussian Basis Sets for Molecular Orbital Calculations”, Elsevier (1986).
[7]    T. H. Dunming and P. J. Hay, “Modern Theoretical Chemistry” Volume 3, Chapter 1, Plenum (1977).
[8]    K. Wendt et al., Z. Phys. A329, 407(1988).
[9]    A. Lombardi et al., Physica C, 235-240, 1651 (1994).
[10]  H. Luttgemeier, V. Florentiev and A. Yakubowskii, “Electronic Properties of High Tc Superconductors and Related Compounds”, Springer-Verlag, Berlin, Proceedings of Conference at Kirchberg, March 1990.
[11]  Jay Shore et al., Phys. Rev. B46, 595 (1992).
[12]  K. Schwarz, C. Ambrose-Draxl and P. Blaha, Phys. Rev. B42, 2051 (1990); Phys. Rev. B44, 5141 (1991).

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