An Overview of the Compton Scattering Calculation

Round 1

Reviewer 1 Report

The paper brings valuable overview on ab initio calculations 
of Compton scattering characteristics in solids including various 
approaches and approximations. The discussion is scientifically 
sound and beneficial. The authors write in the 
conclusions:

"We hope that this work
would be helpful to theoreticians and experimentalists, especially 
for those who work on interdisciplinary branches of science with 
the help of Compton scattering experiments."

Regrettably, this goal is fulfilled only partially. What I miss 
extremely painfully, is a complete lack of any examples. I recommend
very much that the authors demonstrate the effect of all approximations 
studied on Compton characteristics in particular materials, starting, 
for example, with elemental metals as Al, Cu, Nb etc. and also some
ferromagnetic metals, Fe, Co, Ni (magnetic Compton scattering, that's 
a notion!), then some interesting compounds etc.!

Try "magnetic Compton scattering" as a "TITLE" in Web of 
Science, you get 156 hits, the latest one being 

Study of magnetism in Fe doped CoCr2O4 using magnetic Compton scattering and first-principles computations
By: Dashora, Alpa; Suthar, Mahesh; Kumar, Kishor; et al.
JOURNAL OF ALLOYS AND COMPOUNDS   Volume:  824     Article Number: 153883   Published:  MAY 25 2020   

I am sure that the value of the present paper will be enhanced
tremendously when such examples will be given. The calculated
results should also be compared with high-quality experimental 
data to assess the effectiveness of each approximation. I recommend
most enthusiastically that the authors select representatives
of say five classes of materials, starting with elemental metals
and some intermetallics, showing also the effect of magnetism, 
such as found, e.g.,  recently in 

Magnetic Compton profiles of disordered Fe0.5Ni0.5 and ordered FeNi alloys
By: Benea, D.; Minar, J.; Ebert, H.; et al.
PHYSICAL REVIEW B   Volume:  97   Issue:  14     Article Number: 144408   Published:  APR 16 2018, 

in

Temperature dependence of the microscopic magnetization process of Tb12Co88 using magnetic Compton scattering
By: Agui, Akane; Harako, Akino; Shibayama, Akane; et al.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   Volume:  484   Pages:  207-211   Published:  AUG 15 2019  

or in 

Electronic Structure in Heavy Fermion Compound UPd2Al3 through Directional Compton Profile Measurement
By: Koizumi, Akihisa; Kubo, Yasunori; Yamamoto, Etsuji; et al.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   Volume:  88   Issue:  3     Article Number: 034714   Published:  MAR 15 2019

For elements, the authors can use, for illustration, the results
of their recent paper 

Compton scattering energy spectrum for Si and Ge systems
By: Qiao, Chen-Kai; Chi, Hsin-Chang; Lin, Shin-Ted; et al.
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS   Volume:  47   Issue: 4     Article Number: 045202   Published:  FEB 2020

By the way, directional Compton profiles, very important in 
investigations of the electronic structure, are not mentioned 
in the present paper at all!

Then, they should show how the Compton scattering characteristics 
are obtained within the free electron approximation (FEA), 
impulse approximation (IA), incoherent scattering function / incoherent 
scattering factor (ISF) and scattering matrix (SM) approaches and
compare the results of all these approximation with experiment. 
That would be very instructive! And this is what is needed, 
not only a dry description of the formulas without any examples!

Further, the Compton profiles are closely related to the 
positron annihilation angular correlation spectra; see 
e.g. 

Probing the Fermi surface by positron annihilation and Compton scattering
By: Dugdale, S. B.
LOW TEMPERATURE PHYSICS   Volume:  40   Issue:  4   Pages:  328-338   Published:  APR 2014 

Well, again, as it is, the paper is, from my point of view, 
very incomplete. Its may be enhanced very much by showing 
illustrative examples on specific materials how various 
approximations reproduce (or not reproduce) the available 
experimental data. Without giving any examples, I cannot 
recommend this paper for publication in the present form. But it may be reconsidered for publication after a major revision along the lines given 
above.  

 

Author Response

Our Reply to referees and the List of Changed in the revised manuscript is in the PDF file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors give a review paper of theoretical works of Compton scattering. They compare theories of FEA, IA, ISF and SM. This review is very useful for researches. However there is a few unclear points for a reader.

1. Fig.3
Incident enegy wi
Compton peak energy wc
resonant peak energy wr
infrared rise energy wir

wir<wr<wc<wi 

If we fix the incident energy, wi, and energy transfer=delta E,
case a. delta E=wi-wc ->energy of recoil electron in Compton scattering.
case b. delta E=wi-wr ->What is it?
case c. delta E=wi-wir ->What is it?

The case b seems to be RIXS, in which the incident energy should be around resonant energy. However the incident energy may be far from the resonant peak in Fig. 3. 

A reader will be confused.

2. Compton defect
Can author discuss the limit for the Compton defect becoming zero? 
It will be helpful for experiments.

Author Response

Our Reply to Referees' Review Report and the List of Changed in the revised manuscript is in the PDF file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I think that the authors complied with all referees' comments
and better explained their views. The paper benefited a lot from 
the revision.

There is still a need to improve English. Some sentences are 
gramatically incorrect and/or hardly comprehensible. The authors 
should ask a native English speaker to correct the language 
of the article, or maybe the editing service of Materials may
help?

After correcting the English, the paper may be published in 
Materials. 

Author Response

Thanks for referee’s helpful comments.

However, 3 days (which is the time period of minor revision) is too short to finish the language polishing. We can ask editing service for help after the acceptance of this work.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors revised well. However a reader may still confuse.

1. Fig.3
An incident energy depends on the peak (physics). When we discuss wc, wi should be wi>wc. When we discuss the resonant peak, wi should be just above the resonant peak energy. When we discuss the infrared peak, wi goes to zero. However, a reader cannot catch these stories form the text, and will confuse. 
The authors should explain the story of the cover letter in the text.

Author Response

Thanks for referee’s helpful comment. Including these points to the text would make the story better. In this revision, we explain these points in the text according to referee’s suggestion.

More details are in the attachment.

Author Response File: Author Response.pdf