Why some output show 0-by-1

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Sarah
Sarah 2025-3-20
回答： Thorsten 2025-3-20
I am confused about some output has numerical answer, but some show empty system. I did use the same function and the input are similar.
ro = 5;
q = 1.6*10^(-19)
Si_emin = 68.5
Si_emax = 1414
Si_eref = 9.2*10^16
Si_ea = 0.711
Si_n = dp(ro,q,Si_emin,Si_emax,Si_eref,Si_ea)
ro = 5;
q = 1.6*10^(-19)
Si_hmin = 44.9
Si_hmax = 470.5
Si_href = 2.23*10^17
Si_ha = 0.719
Si_p = dp(ro,q,Si_hmin,Si_hmax,Si_href,Si_ha)
ro = 5;
q = 1.6*10^(-19)
GaAs_emin = 500
GaAs_emax = 9400
GaAs_eref = 6*10^16
GaAs_ea = 0.394
GaAs_n = dp(ro,q,GaAs_emin,GaAs_emax,GaAs_eref,GaAs_ea)
ro = 5;
q = 1.6*10^(-19)
GaAs_hmin = 20
GaAs_hmax = 491.5
GaAs_href = 1.48*10^17
GaAs_ha = 0.38
GaAs_p = dp(ro,q,GaAs_hmin,GaAs_hmax,GaAs_href,GaAs_ha)
ro = 5;
q = 1.6*10^(-19)
InP_emin = 0
InP_emax = 5000
InP_eref = 4*10^17
InP_ea = 0.45
InP_n = dp(ro,q,InP_emin,InP_emax,InP_eref,InP_ea)
ro = 5;
q = 1.6*10^(-19)
InP_hmin = 10
InP_hmax = 170
InP_href = 4.87*10^18
InP_ha = 0.62
InP_p = dp(ro,q,InP_hmin,InP_hmax,InP_href,InP_ha)
function x = dp(ro,q,min,max,ref,a)
syms x
eqn = 1/(ro*q*(min+(max-min)/(1+(x/ref)^a)))-x == 0
x = vpasolve(eqn,x)
end
Output：
q = 1.6000e-19
Si_emin = 68.5000
Si_emax = 1414
Si_eref = 9.2000e+16
Si_ea = 0.7110
eqn =
x =
915687197686292.77386563464132068
Si_n =
915687197686292.77386563464132068
q = 1.6000e-19
Si_hmin = 44.9000
Si_hmax = 470.5000
Si_href = 2.2300e+17
Si_ha = 0.7190
eqn =
x =
2758477083642648.6175367991525707
Si_p =
2758477083642648.6175367991525707
q = 1.6000e-19
GaAs_emin = 500
GaAs_emax = 9400
GaAs_eref = 6.0000e+16
GaAs_ea = 0.3940
eqn =
x =
Empty sym: 0-by-1
GaAs_n =
Empty sym: 0-by-1
q = 1.6000e-19
GaAs_hmin = 20
GaAs_hmax = 491.5000
GaAs_href = 1.4800e+17
GaAs_ha = 0.3800
eqn =
x =
Empty sym: 0-by-1
GaAs_p =
Empty sym: 0-by-1
q = 1.6000e-19
InP_emin = 0
InP_emax = 5000
InP_eref = 4.0000e+17
InP_ea = 0.4500
eqn =
x =
Empty sym: 0-by-1
InP_n =
Empty sym: 0-by-1
q = 1.6000e-19
InP_hmin = 10
InP_hmax = 170
InP_href = 4.8700e+18
InP_ha = 0.6200
eqn =
x =
7477430144904512.3068191021258371
InP_p =
7477430144904512.3068191021258371

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回答（1 个）

Thorsten
Thorsten 2025-3-20
It seems that vpasolve cannot solve the equation with the given input to it returns an empty symbol.

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