From: hackbard Date: Mon, 20 Jun 2011 15:37:50 +0000 (+0200) Subject: more ideas added and some formulations X-Git-Url: https://hackdaworld.org/gitweb/?a=commitdiff_plain;h=398c558b399c84c769b7f12c490c626b51b6cc23;p=lectures%2Flatex.git more ideas added and some formulations --- diff --git a/posic/publications/sic_prec_reply02.txt b/posic/publications/sic_prec_reply02.txt index 01a13f6..a72ce7e 100644 --- a/posic/publications/sic_prec_reply02.txt +++ b/posic/publications/sic_prec_reply02.txt @@ -20,18 +20,18 @@ thank you for the feedback to our submission. > resubmit, please include a summary of the changes made, and a detailed > response to all recommendations and criticisms. -We decided to follow your's and the referee's suggestion to merge the +We decided to follow yours and the referee's suggestion to merge the two manuscripts into a single comprehensive manuscript. Please find below the summary of changes and a detailed response to the recommendations of the referee. Most of the criticism is pasted from the previous review justified by -the accusation that we did ignore or not adequatley answered them. -However, we did comment on every single issue and a more adequate +the statement that we did ignore or not adequatley respond to it. +However, we commented on every single issue and a more adequate answer is hindered if the referee does not specify the respective -points of criticism. Thus, some responses are identical to these -included of our previous answer. +points of criticism. Thus, some part of the response might be +identical to our previous one. Sincerely, @@ -40,6 +40,8 @@ Frank Zirkelbach --------------- Response to recommendations ---------------- +TODO: add changes applied due to criticism ... + > I am not happy with these two papers for a multitude of reasons, > and I recommend that the authors rewrite them as a single longer > paper, to eliminate the criticism of serial publication. I do not @@ -49,7 +51,7 @@ Frank Zirkelbach > calculations, and one for the MD ­ this is not how I suggest you > do it, though. -We now combined the two manuscripts into a single comprehensive one. +We now combined the two manuscripts to a single comprehensive one. > do it, though. First, though, the following issues should be > addressed (some are simply pasted from my previous reviews, where @@ -63,19 +65,49 @@ We now combined the two manuscripts into a single comprehensive one. > conclusions on which structure or migration routes are most > likely start to look rather less certain. -Although differences of 0.2 eV in DFT calculations would generally be -acknowledged to be insignificant when being compared to experimental -results or data of other ab initio studies, these differences are -considered to be reliable when comparing results, i.e. differences in -energy, of a systematic study among each other. This is commonly done -as can be seen in a great deal of literature, some of which is cited -in the section of the present manuscript that investigates defect -structures and formation energies. Very often differences less than -0.2 eV are obtained and conclusions on the stability of a particular -structure are derived. +In literature, very often, differences less than 0.2 eV are obtained +in DFT studies and respective conclusions are derived. For instance, +differences in the energy of formation ranging from 0.05 - 0.12 eV are +considered significant enough to conclude on the energetically most +favorable intrinsic defect configurations in Si (PRB 68, 235205 +(2003); PRL 83, 2351 (1999)). This is due to the fact that existing +errors are most probably of the systematic rather than the random +type. The error in the estimate of the cohesive energy is canceled out +since it is likewise wrong in the defect as in the bulk configuration, +which are substracted in the expression of the defect formation +energy. Even if the defect formation energy is overestimated due to a +too small size of the supercell resulting in a non-zero interaction of +the defect with its images, this is likewise true for other defects. +Although the actual value might be wrong, observed differences in +energy, thus, allow to draw conlcusions on the stability of defect +configurations. This is also valid for diffusion barriers, which are +given by differences in energy of different structures. +In fact, differences of 0.2 eV in DFT calculations are considered +insignificant when being compared to experimental results or data of +other ab initio studies. However, the observed differences in energy +within our systematic DFT study are considered reliable. > 2. Why is 216 atoms a large enough supercell ­ many defect > properties are known to converge very slowly with supercell size. + +Of course, choosing a supercell containing 216 atoms constitutes a +tradeoff. It is considered the optimal choice with respect to +computational efficiency and accuracy. + +We would like to point out that, both, single defects as well as +combinations of two defects were investigated in such supercells in +successive calculations. + +For single defects, the size of the supercell should be sufficient. +This is shown in PRB 58, 1318 (1998) predicting convergence of the +vacancy in silicon - the defect assumed to be most critical due to +the flatness of the total energy surface as a function of the ionic +coordinates - for supercells containing more than 128 atomic sites, +where the defect formation energy is already well estimated using +smaller supercells of 64 atomic sites. Thus, convergence of the +formation energies of single defects with respect to the size of the +supercell is assumed. + > They appear to be separating defects by as large a distance as > can be accommodated in the supercell to approximate the isolated > defects, but then they are only separated by a few lattice @@ -83,33 +115,23 @@ structure are derived. > that compare with taking the energies of each defect in a > supercell. -Choosing a 216 atom supercell constitutes a tradeoff, of course. -However, it is considered the optimal choice with respect to both, -computing time and accuracy of the results. - -The convergence of the formation energies of single defects with -respect to the size of the supercell is ensured. For this reason, they -are referred to as single isolated defects. - -It is not our purpose to separate defects by a large distance in order -to approximate the situation of isolated defects. However, we find -that for increasing defect distance configurations appear, which -converge to the energetics of two isolated defects. This is indicated -by the (absolute value of the) binding energy, which is approaching -zero with increasing distance. From this, we conclude a decrease in -interaction, which is already observable for defect separation -distances accessible in our simulations. This is stated now more -clearly in section II of the revised manuscript. (-> Change 6) +Again, we would like to point out that it is not our purpose to +separate defects by a large distance in order to approximate the +situation of isolated defects. However, we find that for increasing +defect distances, configurations appear, which converge to the +energetics of two isolated defects. This is indicated by the (absolute +value of the) binding energy, which is approaching zero with +increasing distance. From this, we conclude a decrease in interaction, +which is already observable for defect separation distances accessible +in our simulations. Nevertheless, the focus is on closely neighbored, interacting defects (for which an interaction with their own image is, therefore, supposed -to be negligible, too). At no time, our aim was to investigate single -isolated defect structures and their properties by increasing the -separation distance of two defects belonging to a a defect -combination. - -A note is added to let the reader know that convergence with respect -to the system size is ensured. (-> Change 2) +to be negligible, too). In fact, combinations of defects exhibiting +equivalent distances were successfully modeled in a supercell +containing 216 atoms in PRB 66, 195214 (2002). At no time, our aim was +to investigate single isolated defect structures and their properties +by a structure with increased separation distance of the two defects. > 3. Constant pressure solves some problems, but creates others ­ > is it really a sensible model of implantation? What differences @@ -123,12 +145,6 @@ However, only small changes in volume were observed and, thus, it is assumed that there is no fundamental difference between calculations in the canonical and isothermal-isobaric ensemble. -Constant volume calculations were not performed and, thus, we cannot -provide concrete differences. - -The fact that there are only small changes in volume is added to the -methodology section. (-> Change 3) - > 4. What method do they use to determine migration paths? How can > they convince us that the calculations cover all possible > migrations paths ­ that is, the paths they calculate are really @@ -168,6 +184,19 @@ minimum energy path may still be missed. (-> Change 4) > need a critical scrutiny, which I am not very convinced by in > this case. +TODO: add idea that elevated temperatures are considered necessary to +deviate the system out of equilibrium, as assumed to be the case in IBS + +you can always add constant to energy. +formation energies are not overestimated +just the migration barriers are +to increase probability of transitions, temperature is increased +occupation of energetically more unfavorable states likewise increased +indeed, sub conf, which is slightly higher than c-si DB, is increased +comparing with experimental findings that suggest c sub for higher +temperatures gives rise to the conclusion that the increased +temperatures are needed to deviate the system out of the ground state! + There is not necessarily a correlation of cohesive energies or defect formation energies with activation energies for migration. Cohesive energies are most often well described by the classical potentials @@ -179,7 +208,7 @@ Since the total binding energy is 'accommodated' within this short distance, which according to the universal energy relation would usually correspond to a much larger distance, unphysical high forces between two neighbored atoms arise. This is explained in detail in the -study of Mattoni et. al. (Phys. Rev. B 76, 224103 (2007)). +study of Mattoni et. al. (PRB 76, 224103 (2007)). Since most of the defect structures show atomic distances below the critical distance, for which the cut-off function is taking effect, @@ -216,3 +245,9 @@ structure, for classical potential as well as ab initio calculations. The arguments discussed above are now explained in more detail in the revised version of our work. (-> Change 1, Change 2) + + +--------------- Summary of changes ---------------- + + +