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[求助]
MgB2超导转变温度
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最近在学习用quantum espresso计算超导转变温度，所以就用比较成熟的MgB2体系作为例子进行实际的计算。但是计算结果与实验值差距很大，实验值是39.3 K，而我最高只能算到4.1 K，想尽各种办法也没能有效提高，不知道是参数设置的不对还是赝势选择有问题。看到有些文献用QE计算的MgB2的转变温度与实验值复合的很好。但是自己计算的就是不对，有这方面经验的虫友请帮忙看一下输入文件，有什么地方是可以改进或是改正的。谢谢了！ 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点会在计算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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