1) How do I make the 'REFERENCES' title start on a new line, AFTER the centred line?
You don't. As you've noticed, revtex4
style inserts a short horizontal rule immediately ahead of the bibliography and does not provide a separate header (such as "REFERENCES"). If you need to use the revtex4
document class, do not modify this very basic and distinctive document layout feature.
2) How can I get the bibitem numbering to be formatted like in square brackets, normal character format? (The prb standards I found say they should be in square brackets)
The revtex4
document class automatically loads the natbib
package. Thus, inserting the instruction
\setcitestyle{numbers,square}
in the preamble will give you non-superscript numbers encased in square brackets.
That said, you should seriously reconsider whether you really have to change the citation call-out style. On page 110 of the user guide of revtex4
class, under section 28.4.2, "prb", one finds:
PRB requires superscript citations.
Thus, if you provide the prb
option to the \documentclass
instruction, you should almost certainly not change the citation call-out style to plain-numbers-encased-in-brackets.
\documentclass[twocolumn,prb]{revtex4} % prb is Physics Review B
\usepackage{amsmath} % need for subequations
\usepackage{graphicx} % need for figures
\usepackage{amssymb}
\usepackage{hyperref} % no need to provide 'pdftex' option
\setcitestyle{numbers,square} % do reconsider whether this is necessary or advisable
\begin{document}
\section{Conclusion}
There are articles that would be missed if only one or two databases\slash sources were searched.\cite{1}
%%\appendix
%%\section*{References}
\begin{thebibliography}{1}
\bibitem{1}
D Baye and P-H Heenen,
J.\ Phys. A:Math.\ Gen., \textbf{19}, 2041--2059 (1986).
\end{thebibliography}
\end{document}
revtex4-1 is here https://ctan.org/pkg/revtex4-1, but you will have to unpack the dtx to get the cls.
You could instead try to substitute the class:
\makeatletter
\declare@file@substitution{revtex4-1.cls}{revtex4-2.cls}
\makeatother
\documentclass{aastex631}
\begin{document}
abc
\end{document}
In any case write to the maintainer of the aastex631 class and ask them not to use an obsolete class.
Best Answer
IF you have your articles as PDFs, you could use the
pdfpages
packageThe inclusion works independently form the pdf it just puts the pages in. One can even specify a header (e.g. pagemark) for the included pages.