flying_lw

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[求助] MgB2超導(dǎo)轉(zhuǎn)變溫度

最近在學(xué)習(xí)用quantum espresso計(jì)算超導(dǎo)轉(zhuǎn)變溫度，所以就用比較成熟的MgB2體系作為例子進(jìn)行實(shí)際的計(jì)算。但是計(jì)算結(jié)果與實(shí)驗(yàn)值差距很大，實(shí)驗(yàn)值是39.3 K，而我最高只能算到4.1 K，想盡各種辦法也沒(méi)能有效提高，不知道是參數(shù)設(shè)置的不對(duì)還是贗勢(shì)選擇有問(wèn)題�？吹接行┪墨I(xiàn)用QE計(jì)算的MgB2的轉(zhuǎn)變溫度與實(shí)驗(yàn)值復(fù)合的很好。但是自己計(jì)算的就是不對(duì)，有這方面經(jīng)驗(yàn)的蟲(chóng)友請(qǐng)幫忙看一下輸入文件，有什么地方是可以改進(jìn)或是改正的。謝謝了！

cat > mgb2.scf.fit.in << EOF
&control
calculation='scf'
restart_mode='from_scratch',
prefix='mgb2',
etot_conv_thr = 1.0d-8
forc_conv_thr = 1.0d-7
pseudo_dir = '$PSEUDO_DIR/',
outdir='$TMP_DIR/'
/
&system
ibrav=  4, celldm(1) =5.8124, celldm(3)=1.1483, nat= 3, ntyp= 2,
ecutwfc =60.0, ecutrho =600,
occupations='smearing', smearing='methfessel-paxton', degauss=0.04,
la2F = .true.,
/
&electrons
conv_thr =  1.0d-8
mixing_beta = 0.7
/
&IONS
/
&CELL
  press = 0.0
  cell_factor = 1.5d0
/
ATOMIC_SPECIES
Mg 24.305 Mg.pw91-np-van.UPF
B  10.811 B.pw91-n-van_ak.UPF
ATOMIC_POSITIONS {crystal}
Mg  0.000000000       0.000000000       0.000000000
B 0.333333333       0.666666667       0.500000000
B 0.666666667       0.333333333       0.500000000
K_POINTS {automatic}
32 32 32 0 0 0
EOF
$ECHO "  running the scf calculation with dense k-point grid...\c"
$PW_COMMAND  < mgb2.scf.fit.in > mgb2.scf.fit.out
check_failure $?
$ECHO "  done"
#
#  SCF at k-mesh good enough for phonons
#
cat > mgb2.scf.in << EOF
&control
calculation='scf'
restart_mode='from_scratch',
prefix='mgb2',
etot_conv_thr = 1.0d-8
forc_conv_thr = 1.0d-7
pseudo_dir = '$PSEUDO_DIR/',
outdir='$TMP_DIR/'
/
&system
ibrav=  4, celldm(1) =5.8124, celldm(3)=1.1483, nat= 3, ntyp= 2,
ecutwfc = 60.0,ecutrho = 600,
occupations='smearing', smearing='methfessel-paxton', degauss=0.04
/
&electrons
conv_thr =  1.0d-8
mixing_beta = 0.7
/
&IONS
/
&CELL
  press = 0.0
  cell_factor = 1.5d0
/
ATOMIC_SPECIES
Mg 24.305 Mg.pw91-np-van.UPF
B  10.811 B.pw91-n-van_ak.UPF
ATOMIC_POSITIONS {crystal}
Mg  0.000000000       0.000000000       0.000000000
B 0.333333333       0.666666667       0.500000000
B 0.666666667       0.333333333       0.500000000
K_POINTS {automatic}
  16 16 16  0 0 0
EOF
$ECHO "  running the scf calculation...\c"
$PW_COMMAND < mgb2.scf.in > mgb2.scf.out
check_failure $?
$ECHO "  done"
#
cat > mgb2.elph.in << EOF
Electron-phonon coefficients for LiCs
&inputph
  iverbosity=1
  tr2_ph=1.0d-12,
  prefix='mgb2',
  fildvscf='mgb2dv',
  amass(1)=24.305,
  amass(2)=10.811,
  outdir='$TMP_DIR/',
  fildyn='mgb2.dyn',
  electron_phonon='interpolated',
  trans=.true.,
  ldisp=.true.
  nq1=8, nq2=8, nq3=8
/
EOF
$ECHO "  running the el-ph calculation...\c"
$PH_COMMAND < mgb2.elph.in > mgb2.elph.out
check_failure $?
$ECHO "  done"
#
# q2r and matdyn
#
cat > q2r.in << EOF
&input
  zasr='simple',  fildyn='mgb2.dyn', flfrc='mgb2.fc', la2F=.true.
/
EOF
$ECHO "  running q2r...\c"
$Q2R_COMMAND < q2r.in > q2r.out
check_failure $?
$ECHO "  done"
#
#
#
cat > matdyn.in.freq << EOF
&input
asr='simple',  amass(1)=24.305, amass(2)=10.811,
flfrc='mgb2.fc', flfrq='mgb2.freq', la2F=.true., dos=.false.
/
  19
  0.000 0.0 0.0    0.0
  0.125 0.0 0.0    0.0
  0.250 0.0 0.0    0.0
  0.375 0.0 0.0    0.0
  0.500 0.0 0.0    0.0
  0.750 0.0 0.0    0.0
  1.000 0.0 0.0    0.0
  0.825 0.125 0.125 0.0
  0.750 0.250 0.250 0.0
  0.625 0.375 0.375 0.0
  0.500 0.500 0.500 0.0
  0.325 0.325 0.325 0.0
  0.250 0.250 0.250 0.0
  0.125 0.125 0.125 0.0
  0.000 0.000 0.000 0.0
  0.125 0.125 0.000 0.0
  0.250 0.250 0.000 0.0
  0.325 0.325 0.000 0.0
  0.500 0.500 0.000 0.0
EOF
$ECHO "  running matdyn for frequency calculation...\c"
$MATDYN_COMMAND < matdyn.in.freq > matdyn.out.freq
check_failure $?
$ECHO "  done"
#
#
#
cat > matdyn.in.dos << EOF
&input
asr='simple',  amass(1)=24.305, amass(2)=10.811,
flfrc='mgb2.fc', flfrq='mgb2.freq', la2F=.true., dos=.true.
fldos='phonon.dos', nk1=10, nk2=10, nk3=10, ndos=50
/
EOF
$ECHO "  running matdyn for a2F(omega) calculation...\c"
$MATDYN_COMMAND < matdyn.in.dos > matdyn.out.dos
check_failure $?
$ECHO "  done"
#
#
#
cat > lambda.in << EOF
50  0.05  1 ! emax (something more than highest phonon mode in THz), degauss, smearing method
1       ! Number of q-points for which EPC is calculated,                                                                                        /其余的q點(diǎn)會(huì)在計(jì)算Tc是加上。
   0.000000  0.000000  0.000000 1
elph. 0.000000. 0.000000. 0.000000
0.10                   ! \mu the Coloumb coefficient in the modified
                     ! Allen-Dynes formula for T_c (via \omega_log)
EOF
$ECHO "  running lambda.x for lambda calculation...\c"
$LAMBDA_COMMAND < lambda.in > lambda.out
check_failure $?
$ECHO "  done"

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1樓 2014-05-14 08:52:14

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ccmin4

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什么是cell_factor?

贊一下

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對(duì)不起

2樓2014-05-28 13:47:00

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flying_lw

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引用回帖:

2樓: Originally posted by ccmin4 at 2014-05-28 13:47:00
什么是cell_factor?

cell_factor:
Used in the construction of the pseudopotential tables.
It should exceed the maximum linear contraction of the
cell during a simulation.

這是QE網(wǎng)站上關(guān)于輸入?yún)?shù)的介紹。具體的我也不是特別理解。

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3樓2014-06-24 07:32:39

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Robin122R

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樓主解決了嗎，我也遇到這個(gè)問(wèn)題了，celldm(3)=1.1483這個(gè)值對(duì)不對(duì)，文獻(xiàn)中寫(xiě)的c軸晶格常數(shù)是3.524艾，那celldm(3)就應(yīng)該是6.65939438，但是我看好多關(guān)于MgB2的例子中celldm(3)都是等于1.1483，不知道是不是我想錯(cuò)了

贊一下

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4樓2020-09-25 17:02:08

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