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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.2015-11-27T11:45:38ZCCS 120A Chicana and Chicano Roles in the American Political System Section 1-2
http://hdl.handle.net/10211.3/149779
CCS 120A Chicana and Chicano Roles in the American Political System Section 1-2
Ortiz, Isidro
Syllabus for CCS 120A sections 1 and 2
2015-10-08T00:00:00ZFirst-principles Calculation of the Conformation and Electronic Structure of Polyparaphenylene
http://hdl.handle.net/10211.3/158302
First-principles Calculation of the Conformation and Electronic Structure of Polyparaphenylene
Miao, Maosheng; Van Camp, P. E.; Van Doren, V. E.; Ladik, J. J.; Mintmire, J. W.
In this article, an all-electron first-principles total energy calculation with Gaussian-type functions for the wave functions, for the exchange correlation potential, and for the charge density has been applied for single chains of polyparaphenylene (PPP). A local-density approximation within a helical band structure approach has been used. The calculated torsional potential shows a minimum at the torsion angle of 34.8 degrees. The internal coordinates were optimized in the equilibrium conformation and are in good agreement with experimental and other theoretical results. The calculated direct band gap is 2.54 eV compared with the experimental result from UPS spectra of 3.4 eV for the gas phase. The band structure strongly depends on the conformation which suggests that the electronic properties can be modified in a wide range through doping or addition of side groups. (C) 1998 American Institute of Physics. [S0021-9606(98)30743-6].
1998-01-01T00:00:00ZCalculation of the Total Energy Per Unit Cell and of the Band Structures of the Five Nucleotide Base Stacks Using the Local-density Approximation
http://hdl.handle.net/10211.3/158301
Calculation of the Total Energy Per Unit Cell and of the Band Structures of the Five Nucleotide Base Stacks Using the Local-density Approximation
Zhang, M.-L.; Miao, Maosheng; Van Doren, V. E.; Ladik, J. J.; Mintmire, J. W.
All-electron first-principles total energy electronic structure calculations were carried out for single chains of four nucleotide base stacks (composed of adenine, thymine, guanine, and cytosine, respectively) in the DNA B conformation (3.36 Angstrom stacking distance and 36 degrees screw angle theta) using the local-density approximation (LDA) within a helical band structure approach. A uracil stack was also computed in the DNA B conformation and compared with the results obtained for the four DNA base stacks. The total energies per unit cell as a function of the stacking distance (at fixed screw angle theta = 36 degrees) and of the screw angle (at d = 3.36 Angstrom) show in most cases rather good agreement with the experiment. As expected with LDA calculations, the band gaps were underestimated by nearly 50% compared to experimentally suggested values. Finally, some suggestions are given for the improvement of the band structures of the nucleotide base stacks. (C) 1999 American Institute of Physics. [S0021-9606(99)30342-1].
1999-01-01T00:00:00ZDensity functional calculations on the structure of crystalline polyethylene under high pressures
http://hdl.handle.net/10211.3/158300
Density functional calculations on the structure of crystalline polyethylene under high pressures
Miao, Maosheng; Zhang, M.-L.; Van Doren, V. E.
The geometrical structures of the crystalline polyethylene under several different external pressures up to 10 GPa are optimized by a pseudopotential plane wave density functional method. Both local density (LDA) and generalized gradient (GGA) approximations for exchange-correlation energy and potential are used. It is found that LDA heavily underestimate the geometry parameters under ambient pressure but GGA successfully correct them and get results in good agreements with the experimental geometry. The calculated GGA volume is about 94 Angstrom (3) in comparison with the x-ray scattering value of about 92 Angstrom (3) and the neutron scattering value of 88 Angstrom (3). The bulk and Young's modulus are calculated by means of several different methods. The Young's modulus along the chain ranges from about 350 to about 400 GPa which is in good agreement with the experimental results. But the bulk modulus is several times larger than those of experiments, indicating a different description of the interchain interactions by both LDA and GGA. The band structures are also calculated and their changes with the external pressure are discussed. (C) 2001 American Institute of Physics.
2001-01-01T00:00:00Z