You are here
Firstprinciples study of metastable phases and structural anomalies of Fe, Al, Zn, and Cd under pressure
 Date Issued:
 2008
 Summary:
 Stable and metastable phases of Fe and Al and structural anomalies of Zn and Cd have been studied by epitaxial Bain path (EBP) and minimum path (MNP) firstprinciples procedures, based on finding equilibrium structures from minimizing the Gibbs free energy G with respect to structure at a given hydrostatic pressure p and temperature T . The main accomplishments are as follows. (1) This dissertation illustrates the effectiveness of the MNP procedure for finding stable and metastable phases of an element by studying four Bravais phases of Fe including bodycentered tetragonal (bct), bodycentered cubic (bcc), facecentered cubic (fcc) and rhombohedral (rh) phases. The determination of absolute stability using MNP is new; MNP finds all the elastic constants cjj of a given state and the eigenvalues of the elastic constants matrix, which determine the absolute stability of the state.
Title:  Firstprinciples study of metastable phases and structural anomalies of Fe, Al, Zn, and Cd under pressure. 
155 views
29 downloads 

Name(s): 
Apostol, Florin. Florida Atlantic University, Degree grantor Charles E. Schmidt College of Science Department of Physics 

Type of Resource:  text  
Genre:  Electronic Thesis Or Dissertation  
Date Issued:  2008  
Publisher:  Florida Atlantic University  
Physical Form:  electronic  
Extent:  xv, 142 p. : ill.  
Language(s):  English  
Summary:  Stable and metastable phases of Fe and Al and structural anomalies of Zn and Cd have been studied by epitaxial Bain path (EBP) and minimum path (MNP) firstprinciples procedures, based on finding equilibrium structures from minimizing the Gibbs free energy G with respect to structure at a given hydrostatic pressure p and temperature T . The main accomplishments are as follows. (1) This dissertation illustrates the effectiveness of the MNP procedure for finding stable and metastable phases of an element by studying four Bravais phases of Fe including bodycentered tetragonal (bct), bodycentered cubic (bcc), facecentered cubic (fcc) and rhombohedral (rh) phases. The determination of absolute stability using MNP is new; MNP finds all the elastic constants cjj of a given state and the eigenvalues of the elastic constants matrix, which determine the absolute stability of the state.  
Summary:  (2) We have extended our search for stable and metastable phases from zero temperature to finite temperature, which requires the calculations of the Debye temperature Od from cjj in the case of no symmetry. The Debye theory is modified by introducing a parameter B2 that gives the fraction of the full Debye zeropoint energy possessed by the actual dispersive mode frequencies. The value of the lattice parameter of fcc Al at low temperatures,a(T) , is shown to be accurately determined by the modified Debye theory of lattice vibrations and firstprinciples total energy band calculations with the MNP procedure. (3) The existence of structural anomalies in hcp Zn and Cd has been shown from firstprinciples totalenergy calculations using WIEN2k with the EBP procedure.  
Summary:  Evaluation of the pressure dependence of various elastic quantities which are much more sensitive to the anomaly shows that the anomalies in hcp Zn and hcp Cd exist over a considerable range of pressure; several abrupt changes in the electron distribution are thereby indicated in that pressure range. (4) Calculations on the zonecenter transverse optical phonon frequencies Vto(p) of hcp Zn, which found oscillatory behavior of Vto(p) in the pressure range of the anomalies, support the conclusions made in (3) on the structural anomalies. Based on this dissertation research four papers have been published in refereed journals.  
Identifier:  302357145 (oclc), 186334 (digitool), FADT186334 (IID), fau:2882 (fedora)  
Note(s): 
by Florin Apostol. Thesis (Ph.D.)Florida Atlantic University, 2008. Includes bibliography. Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web. 

Subject(s): 
Epitaxy Mathematical physics Metals  Electric properties Phase transformation (Statistical physics) 

Persistent Link to This Record:  http://purl.flvc.org/FAU/186334  
Use and Reproduction:  http://rightsstatements.org/vocab/InC/1.0/  
Host Institution:  FAU 