Hello everyone, I use the input file below to get C4H8 biradical. First, I get the initial guess wave function through UDFT single point energy calculation ，which needs “SCF_GUESS_MIX” and “STABILITY_ANALYSIS” to ensure the stability of the initial guess wave function. Then, I carried out structural optimization and frequency calculation, and both steps read the prior initial guess wave function by “SCF_GUESS = read”. Unfortunately, the result converges to the structure of cyclobutane rather than the C4H8 diradical. Could you help me check what’s wrong with the input file？Do you have any suggestion on how to calculate diradicals? Look forward to your reply, thank you

$molecule

0 1

C -0.92219100 1.49609700 0.46979900

C -0.80401500 0.21210200 -0.28769100

C 0.21213400 -0.80400300 0.28771600

C 1.49608600 -0.92216400 -0.46985100

H -1.74223400 2.17255800 0.27078800

H -0.09268100 1.86292200 1.06116000

H -0.54327100 0.40987500 -1.34002800

H -1.79333800 -0.25598800 -0.33446900

H -0.25592100 -1.79333500 0.33456200

H 0.40995700 -0.54319200 1.34002800

H 1.86306800 -0.09247100 -1.06086100

H 2.17240500 -1.74240000 -0.27115200

$end

$rem

BASIS = 6-311G**

GUI = 2

METHOD = M06-2X

UNRESTRICTED = true

SCF_GUESS_MIX = 2

SYM_IGNORE = true

STABILITY_ANALYSIS = true

$end

@@@

$molecule

read

$end

$rem

JOB_TYPE opt

METHOD M06-2X

BASIS 6-311G**

UNRESTRICTED = true

SCF_GUESS = read

SYM_IGNORE = true

SCF_MAX_CYCLES = 250

$end

@@@

$molecule

read

$end

$rem

JOB_TYPE freq

METHOD M06-2X

BASIS 6-311G**

UNRESTRICTED = true

SCF_GUESS = read

SCF_MAX_CYCLES = 250

$end