1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<!--Converted with LaTeX2HTML 2019.2 (Released June 5, 2019) -->
<HTML lang="EN">
<HEAD>
<TITLE>4.2 Calculation of interatomic force constants in real space</TITLE>
<META NAME="description" CONTENT="4.2 Calculation of interatomic force constants in real space">
<META NAME="keywords" CONTENT="user_guide">
<META NAME="resource-type" CONTENT="document">
<META NAME="distribution" CONTENT="global">
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8">
<META NAME="viewport" CONTENT="width=device-width, initial-scale=1.0">
<META NAME="Generator" CONTENT="LaTeX2HTML v2019.2">
<LINK REL="STYLESHEET" HREF="user_guide.css">
<LINK REL="next" HREF="node9.html">
<LINK REL="previous" HREF="node7.html">
<LINK REL="next" HREF="node9.html">
</HEAD>
<BODY >
<!--Navigation Panel-->
<A
HREF="node9.html">
<IMG WIDTH="37" HEIGHT="24" ALT="next" SRC="next.png"></A>
<A
HREF="node6.html">
<IMG WIDTH="26" HEIGHT="24" ALT="up" SRC="up.png"></A>
<A
HREF="node7.html">
<IMG WIDTH="63" HEIGHT="24" ALT="previous" SRC="prev.png"></A>
<A ID="tex2html69"
HREF="node1.html">
<IMG WIDTH="65" HEIGHT="24" ALT="contents" SRC="contents.png"></A>
<BR>
<B> Next:</B> <A
HREF="node9.html">4.3 Calculation of electron-phonon</A>
<B> Up:</B> <A
HREF="node6.html">4 Using PHonon</A>
<B> Previous:</B> <A
HREF="node7.html">4.1 Single-q calculation</A>
<B> <A ID="tex2html70"
HREF="node1.html">Contents</A></B>
<BR>
<BR>
<!--End of Navigation Panel-->
<H2><A ID="SECTION00052000000000000000">
4.2 Calculation of interatomic force constants in real space</A>
</H2>
<P>
First, dynamical matrices are calculated and saved for a suitable uniform
grid of <B>q</B>-vectors (only those in the Irreducible Brillouin Zone of the
crystal are needed). Although this can be done one <B>q</B>-vector at the
time, a
simpler procedure is to specify variable <TT>ldisp=.true.</TT> and to set
variables <TT>nq1</TT>, <TT>nq2</TT>, <TT>nq3</TT> to some suitable
Monkhorst-Pack grid, that will be automatically generated, centered at
<IMG STYLE="height: 1.52ex; vertical-align: -0.55ex; " SRC="img1.png"
ALT="$\bf q$"> = 0.
<P>
Second, code <TT>q2r.x</TT> reads the dynamical matrices produced in the
preceding step and Fourier-transform them, writing a file of Interatomic Force
Constants in real space, up to a distance that depends on the size of the grid
of <B>q</B>-vectors. Input documentation in the header of <TT>PHonon/PH/q2r.f90</TT>.
<P>
Program <TT>matdyn.x</TT> may be used to produce phonon modes and
frequencies at any <B>q</B> using the Interatomic Force Constants file as input.
Input documentation in the header of <TT>PHonon/PH/matdyn.f90</TT>.
<P>
See Example 02 for a complete calculation of phonon dispersions in AlAs.
<P>
<BR><HR>
</BODY>
</HTML>
|
