Nomenclature groups in different pages

Question

I wish I could have the groups inside nomenclature in different pages each and their titles centered. So far I tried the following MWE:

\documentclass[10pt,a4paper]{article}

\usepackage[utf8]{inputenc}
\usepackage{etoolbox}
\usepackage{nomencl}
\makenomenclature

\renewcommand\nomgroup[1]{%
    \item[\centering\normalsize\bfseries
    \ifstrequal{#1}{A}{%
        \MakeUppercase{List of Abbreviations and Acronyms}%
    }{%
        \ifstrequal{#1}{S}{\MakeUppercase{List of Symbols}}{}}%
    ]\thispagestyle{empty}}

\renewcommand{\nomname}{}

\begin{document}
    \nomenclature[A]{H2O}{Water}
    \nomenclature[A]{CO2}{Chemical 1}
    \nomenclature[A]{CO}{Chemical 2}
    \nomenclature[A]{HC}{Chemical 3}
    \nomenclature[A]{kWp}{kilowatt-peak}
    \nomenclature[S]{EPE}{Research Electrical Company}

    \printnomenclature[1cm]
\end{document}

I got this:

But I wish I have them in different pages and the titles centered like this:

The solution here seem to solve the different pages problem but it doesn't solve the title centered. Could anyone help me please?

Answer 1

The issue here is that command \nomgroup needs to be an \item to be printed in the nomenclature. Therefore your try with \centering (that is inside \item[] could not work.

A workaround is to use the following code (see both used \hfill outside the label definition of \item; important code marked with <======):

 \item[]% <=============================================================
    {\hfil\normalsize\bfseries % <======================================
    \ifstrequal{#1}{A}{%
        \MakeUppercase{List of Abbreviations and Acronyms}%
    }{%
        \ifstrequal{#1}{S}{\MakeUppercase{List of Symbols}}{}%
    }%
    \hfil} % <==========================================================

Please see that this kind of centering is not really perfect because the length of the label is not included ... That is the reason I call it a workaround ...

With the following complete code

\documentclass[10pt,a4paper]{article}

\usepackage[utf8]{inputenc}
\usepackage{etoolbox}

\usepackage{showframe}% <============ to visualize text area and margins

\usepackage{nomencl}
\makenomenclature

\newif\iffirstglossary\firstglossarytrue
\renewcommand\nomgroup[1]{%
  \iffirstglossary
    \firstglossaryfalse
  \else
    \clearpage
  \fi
 \item[]% <=============================================================
    {\hfil\normalsize\bfseries % <======================================
    \ifstrequal{#1}{A}{%
        \MakeUppercase{List of Abbreviations and Acronyms}%
    }{%
        \ifstrequal{#1}{S}{\MakeUppercase{List of Symbols}}{}%
    }%
    \hfil} % <==========================================================
%] % <==================================================================
  \thispagestyle{empty}}

\renewcommand{\nomname}{}


\begin{document}

\nomenclature[A]{H2O}{Water}
\nomenclature[A]{CO2}{Chemical 1}
\nomenclature[A]{CO}{Chemical 2}
\nomenclature[A]{HC}{Chemical 3}
\nomenclature[A]{kWp}{kilowatt-peak}
\nomenclature[S]{EPE}{Research Electrical Company}

\printnomenclature[1cm]
\end{document}

you get the following result: